La bileto al la koncerto kostis pli ol mi pensis.

La is the definite article, like the in English.

So La bileto means the ticket, not just a ticket or ticket in general.

In this sentence, the speaker is talking about a specific ticket, so la is natural. Esperanto uses la much like English uses the, though Esperanto has no separate word for a/an.

Esperanto nouns always end in -o.

So:

• bilet- = the word root
• bileto = ticket

This regular noun ending is one of the basic patterns of Esperanto grammar.

Yes, al usually means to, but in Esperanto it can also show destination or connection toward something.

So bileto al la koncerto literally looks like ticket to the concert. This is a normal way to say what event the ticket is for.

English also says a ticket to the concert, so this matches quite well.

You may also sometimes see por in similar contexts, but al la koncerto is very natural here.

Because la bileto is the subject of the sentence, not the direct object.

In Esperanto, the -n ending marks a direct object. Here, the ticket is the thing doing the action of kostis:

• La bileto ... kostis ... = The ticket ... cost ...

Since it is the subject, it stays bileto, not bileton.

The verb is kosti = to cost.

Esperanto verbs have very regular endings:

• -as = present
• -is = past
• -os = future
• -us = conditional
• -u = command / jussive
• -i = infinitive

So:

• kostas = costs
• kostis = cost / did cost
• kostos = will cost

Here kostis is past tense, because the speaker is talking about what the ticket cost.

Because pli ol means more than.

• pli = more
• ol = than

So:

• pli ol mi pensis = more than I thought

This is a standard comparison pattern in Esperanto:

• pli ol = more than
• malpli ol = less than
• tiom ... kiom = as ... as

Esperanto often allows the object of pensis to be left understood when the meaning is obvious.

In English, we also say:

• It cost more than I thought

We do not need to say:

• It cost more than what I thought it would cost

Esperanto works similarly here. The missing idea is understood from context: the speaker means more than I thought it would cost.

If you wanted to make it more explicit, you could say something longer, but the shorter form is completely normal.

Yes, it is basically a comparison clause.

The full idea is something like:

• pli ol mi pensis [ke ĝi kostus]

That longer version would mean something like more than I thought [that it would cost].

But Esperanto, like English, often leaves out repeated information when it is obvious.

So ol mi pensis is a natural shortened clause.

Because koncerto is also a noun, and here it refers to a specific concert.

So:

• la bileto = the ticket
• la koncerto = the concert

Esperanto does not usually let one la cover two separate nouns in a phrase like this. Each noun gets its own article if needed.

Yes, that would also be understandable and natural.

The difference is slight:

• bileto al la koncerto emphasizes the ticket as giving access to the concert
• bileto por la koncerto emphasizes the ticket as being for the concert

In many situations, both work. In this sentence, al la koncerto is a very normal choice.

Because Esperanto verbs show tense directly in the verb ending, so no extra helper word is needed.

English often uses auxiliary verbs like do, have, or will. Esperanto usually does not.

So:

• kostis already means cost / did cost
• pensis already means thought / did think

The tense is built right into the verb.

Esperanto word order is fairly flexible, but this order is the most natural and straightforward.

The sentence follows a simple pattern:

• La bileto al la koncerto = subject phrase
• kostis = verb
• pli ol mi pensis = comparison phrase

You could move things around for emphasis, but the original version is the clearest neutral order for most situations.

Sometimes, but not always.

• pensi = to think
• opinii = to have an opinion / to suppose / to believe

In a sentence like this, mi pensis is the most natural match for English I thought.

Mi opiniis is possible in some contexts, but it can sound a little more formal or more like I was of the opinion. For everyday speech, pensis is usually the better choice here.