nehuda wo mitara omotta yori takakatta node, sono tiizu ha kawanakatta.

Here, 見たら means when I looked at it or after seeing it.

It comes from:

• 見る = to see / to look
• 見た = saw / looked
• 見たら = when I saw / when I looked

Although ～たら is often introduced as a conditional (if), with a past action like this it very often means when or after in narration.

So:

• 値札を見たら = when I looked at the price tag

を marks the direct object of the verb.

Since 見る means to look at / to see, the thing being looked at takes を:

• 値札を見た = looked at the price tag

So 値札 is the thing the speaker saw.

The subject is omitted, but it is understood to be the speaker: I.

Japanese very often leaves out subjects when they are obvious from context. So this sentence naturally means:

• (I) looked at the price tag
• (I) realized it was more expensive than I thought
• (I) didn’t buy that cheese

You do not need to say 私は unless you want extra emphasis or contrast.

思ったより means than I thought or more literally than what I had thought.

Breakdown:

• 思った = thought
• より = than

This is a very common comparison pattern:

• 思ったより高い = more expensive than I thought
• 思ったより難しい = harder than I thought
• 思ったより小さい = smaller than I thought

Japanese often leaves out words that English would include. So even though English says more expensive than I thought it would be, Japanese can simply say 思ったより高かった.

高かった is the past form of the い-adjective 高い.

• 高い = expensive / high
• 高かった = was expensive / was high

The sentence is describing what the speaker found at that moment in the past, so the past form is natural:

• 思ったより高かった = it was more expensive than I thought

Even though English sometimes uses present in general statements, Japanese often uses the past here because the whole event happened in the past.

The subject is omitted.

In English, we would usually say it was more expensive than I thought. In Japanese, the listener understands from context what was expensive.

Depending on how you think about it, the omitted subject is either:

• そのチーズ = that cheese
  or
• its price

Japanese commonly says a thing is 高い to mean its price is high:

• このチーズは高い = this cheese is expensive

So there is no problem even though price is not explicitly repeated.

Because 高い literally means high, and Japanese uses high for prices just like English does in expressions such as high prices.

So:

• 値段が高い = the price is high
• このチーズは高い = this cheese is expensive

Likewise:

• 安い = cheap / inexpensive

So in this sentence, 高かった means was expensive, not that the cheese was physically tall or high up.

ので means because or so, but it sounds a bit more explanatory and a bit softer than から.

• 高かったので、買わなかった = because it was expensive, I didn’t buy it

Compared with から:

• から can sound more direct, personal, or assertive
• ので often sounds smoother and more matter-of-fact

So this sentence has a natural explanatory tone: the speaker is simply giving the reason.

Both are possible, but は gives a different nuance.

• そのチーズを買わなかった = I didn’t buy that cheese
• そのチーズは買わなかった = as for that cheese, I didn’t buy it / I didn’t buy that cheese

Using は makes そのチーズ the topic and can add a slight sense of contrast, such as:

• maybe I bought something else, but that cheese I didn’t buy

So は is very natural here, especially when talking about one item among others.

その means that and refers to something already identified in the situation or conversation.

The basic set is:

• この = this (near the speaker)
• その = that (near the listener / already mentioned / the one in question)
• あの = that over there (away from both)

In this sentence, そのチーズ means that cheese—the cheese whose price tag the speaker just looked at.

Yes, but it is usually unnecessary.

You could say:

• 私は値札を見たら、思ったより高かったので、そのチーズは買わなかった。

But Japanese normally omits 私は when the subject is obvious. Leaving it out sounds natural and less repetitive.

Adding 私は would only be useful if you wanted emphasis, contrast, or clearer context.