Translation:Although it is more convenient to live in the city, it is also more expensive.
I got this sentence with the word tile format, too. It does make it rather confusing. ;-) It's rather difficult to know which clause Duo wants the "rather" in, and where they want the "more."
Intuitively, I always want to say "comparatively" when I see 比较, but it doesn't always make for the best English translation.
While the "but" is mandatory in Chinese, it's not in English. In fact, it seems to be considered grammatically incorrect to use "although" and "but/however" in the same sentence. https://resources.allsetlearning.com/chinese/grammar/Expressing_%22although%22_with_%22suiran%22_and_%22danshi%22