Learn Hardcore Indonesian: Menurut saya, harga tiket itu tidak sepadan dengan kualitas konser. - In my opinion, that ticket price is not equal to the quality of the concert.

It is a neutral, quite common way to introduce an opinion, especially in semi-formal or polite speech.
It sounds a bit more objective or measured, like “from my point of view”.

Comparison:

saya pikir = I think (more like a direct mental opinion, can sound slightly more casual/straightforward).
saya rasa = I feel / I think (can express a mix of thought and feeling; often a bit softer).

All three can work in many everyday situations, but:

In something like a review, complaint, or polite disagreement, menurut saya is very natural and slightly more formal/polite than saya pikir.

Does menurut saya always have to go at the beginning of the sentence, and is the comma necessary?

No, it doesn’t have to be at the beginning, and the comma is a writing convention rather than a grammatical rule.

Your sentence:

Menurut saya, harga tiket itu tidak sepadan dengan kualitas konser.
- This sounds like: In my opinion, the ticket price is not worth the quality of the concert.

You could also say:

Harga tiket itu, menurut saya, tidak sepadan dengan kualitas konser.
Harga tiket itu tidak sepadan dengan kualitas konser, menurut saya.

All are grammatically correct; the difference is just emphasis and style:

At the beginning: you frame the whole statement as an opinion right away.
In the middle or end: you add your opinion as clarification or softening.

The comma simply marks a pause in written Indonesian. In casual writing, some people might omit it, but with or without the comma, the spoken rhythm usually has a small pause there.

What is the function of itu in harga tiket itu? Why not just say harga tiket?

Itu here works like that / the and helps make the noun phrase more specific.

harga tiket = ticket price (in general; not clearly tied to a specific concert/situation).
harga tiket itu = that ticket price / the ticket price (we’re talking about).

In context, itu usually refers to something already known in the conversation or situation, such as:

the price of a concert everyone is currently talking about, or
the price on a poster you’re both looking at.

Leaving out itu isn’t wrong, but it sounds more general. With itu, you sound like you’re judging a specific ticket price that both speaker and listener already know about.

Is harga tiket singular or plural? How would you say “ticket prices” in Indonesian?

Indonesian does not mark singular/plural in the same way English does. Harga tiket can mean:

ticket price (singular)
or
ticket prices (plural), depending on context.

If you want to emphasize plural, you can make it explicit:

harga-harga tiket = ticket prices (reduplicated harga signals plurality).
harga tiketnya can still be singular or plural, but often refers to the price(s) of the ticket(s) in this context.

However, in most real-life situations, just harga tiket or harga tiket itu is enough; listeners understand singular vs plural from context.

Why is tidak used here instead of bukan?

Tidak and bukan both mean not, but they are used with different types of words:

tidak negates verbs and adjectives.
bukan negates nouns and noun phrases.

In the sentence:

tidak sepadan: sepadan is an adjective (roughly “equivalent / commensurate / proportionate”).

So you must use tidak:

harga tiket itu tidak sepadan ✅

If you were negating a noun, you would use bukan, for example:

Itu bukan harga tiket. = That is not a ticket price.

What does sepadan mean here, and how is tidak sepadan dengan used?

Sepadan is an adjective that means roughly:

equivalent, proportionate, on the same level, matching in value or quality.

In the phrase:

tidak sepadan dengan = not equivalent to / not commensurate with / not worth (compared to)

Your sentence:

harga tiket itu tidak sepadan dengan kualitas konser
≈ that ticket price is not commensurate with the quality of the concert
(in natural English: the ticket price wasn’t worth the quality of the concert).

Common patterns:

X sepadan dengan Y = X is on the same level as Y.
X tidak sepadan dengan Y = X is not on the same level as Y.

So:

Gajinya tidak sepadan dengan pekerjaannya.
= The salary is not in proportion to the work.

Could you use other words instead of sepadan here, like sebanding or sesuai? Are they interchangeable?

You can use other adjectives, and they are similar but not always perfectly interchangeable.

Some close alternatives:

sebanding (dengan)
- Very close in meaning to sepadan: proportionate / comparable.
- Harga tiket itu tidak sebanding dengan kualitas konser.
  ≈ the same meaning as the original sentence; very natural.
sesuai (dengan)
- Means “in accordance with / appropriate for / matches”.
- Harga tiket itu tidak sesuai dengan kualitas konser.
  = The ticket price doesn’t match the concert’s quality.
- Slightly more about “fitting” or “matching expectations” than about strict value equivalence.
seimbang (dengan)
- More about “balanced”.
- Less common in this price–quality context than sepadan or sebanding, but possible.

In this sentence, sepadan and sebanding are the most natural if you want the sense “not worth it in terms of value vs quality”.

Why is dengan used after sepadan? Can you drop it?

Sepadan usually takes a comparison phrase with dengan:

sepadan dengan X = proportionate to X.

So:

harga tiket itu tidak sepadan dengan kualitas konser
= the price is not proportionate to the concert’s quality.

Here, dengan works like with / to in English.
In standard usage, you keep dengan; dropping it would sound incomplete or unnatural:

harga tiket itu tidak sepadan kualitas konser ❌ (sounds wrong)
harga tiket itu tidak sepadan dengan kualitas konser ✅

Think of sepadan dengan as a chunk: they typically go together.

Why is it kualitas konser and not something like konser kualitas? How does this noun–noun structure work?

In Indonesian, the typical order for noun + noun combinations is:

main noun
- modifier noun

So:

kualitas konser
= literally quality concert, but understood as
= the quality of the concert.

Comparisons:

harga tiket = price (of) ticket / ticket price
warna baju = color (of) shirt / shirt color

You normally do not reverse the order (konser kualitas). The second noun (konser) acts like a specifier or “of …” phrase in English.

What is the formality level of this whole sentence? Would it be natural in everyday conversation?

The sentence:

Menurut saya, harga tiket itu tidak sepadan dengan kualitas konser.

is neutral to slightly formal, and very natural in many contexts:

spoken reviews (e.g., talking about a concert with friends),
written reviews (blog posts, comments, ratings),
polite conversation or complaints.

In very casual speech, people might say something less formal, like:

Menurut saya, tiketnya nggak worth it sama konsernya.
(mixing Indonesian with English worth it and using nggak instead of tidak)

But your original sentence is perfectly natural and appropriate for most everyday situations, including polite ones.

Could you shorten the sentence and still be understood, for example by omitting some nouns?

Yes, in context you can shorten it, especially if it’s already clear what you’re talking about.

For example:

Menurut saya, tiketnya tidak sepadan.
- Literally: In my opinion, the ticket (price) isn’t equivalent (to it).
- Here sepadan is understood as “not worth it” given the earlier context (concert).
Menurut saya, harganya tidak sepadan.
- In my opinion, the price isn’t worth it.

These are natural in conversation when both sides already know:

which ticket or price,
which concert or event,

so you don’t need to repeat kualitas konser explicitly.