Learn Hardcore Japanese: kuukiseizyouki no syuuridai ha omotta yori takakatta desu. - The repair cost of the air purifier was higher than I expected.

空気 (くうき) = “air”
清浄 (せいじょう) = “purification” or “clean”
機 (き) = “machine” or “device”
Put together, it means “air purification machine,” i.e. an “air purifier.”

How does the particle の function in 空気清浄機の修理代?

Here の marks a genitive (possessive or “of”) relationship between two nouns:

空気清浄機の修理代 = “the repair cost of the air purifier.”

What does 修理代 mean, and what are its parts?

修理代 (しゅうりだい) also breaks down:

修理 (しゅうり) = “repair”
代 (だい) = “fee,” “price,” or “cost”
So 修理代 is the “repair fee/cost.”

Why is 修理代 marked with は instead of が?

は is the topic marker, shifting the focus to “as for the repair cost (of the air purifier)….” If you used が, you’d be simply identifying or introducing it. Using は sets it up for comment (in this case, “it was higher than I thought”).

What does 思ったより express and how is it constructed?

思ったより means “than I thought.” It’s a comparative structure:

思った = “(I) thought” (past tense of 思う)
より = “than”
Together, 思ったより = “than I’d thought” or “more than I expected.”

Why is 高かった in the past tense here?

Using the past tense 高かった rather than 高い indicates that you’re talking about a completed experience or fact: you already saw the bill, and it turned out to be expensive.

What role does です play after 高かった?

です adds politeness. The adjective phrase 高かった is already grammatically complete, but です makes the statement more polite, as in “it was expensive, you know.”

Why is 空気清浄機 not the topic, but 修理代 is?

In this sentence, the speaker isn’t commenting on the air purifier itself but on its repair cost. By placing は after 修理代, they signal that “the repair cost” is the topic under discussion, not “the air purifier.”

Why isn’t there an explicit subject (like “I” or “the bill”) in the sentence?

Japanese often omits obvious subjects. Here it’s understood from context that the speaker is talking about their repair cost. There’s no need to say 私の or 請求書が, since listeners infer “my bill” or “my experience.”

Could you say 思っていたより高かったです instead of 思ったより高かったです? What’s the nuance?

Yes. 思っていたより uses the past-continuous/experiential sense (“than I had been thinking”), implying you’d been expecting a certain cost until just before seeing the actual price. 思ったより is a bit more instantaneous: “upon seeing it, I thought, ‘this is higher than I expected.’” Both are natural, with only a subtle difference in how you frame your prior expectation.