My answer is (B). It took me 02:18.
(A) Anything wrong with "it"? No. "it" refers to "skiing".
Anything wrong with "
even"? I take issues with "even" as it indicates that "900 euros for one week" is shockingly prohibitive. It might be expensive, but not to the extent to merit the use of "even". (I realized the question was authored a long time ago, so 900 euros then might be a larger fortune. I also realized that I could not afford it then or now. Still, do not like "even". )
But all five options use "even", so I have to accept its use
even if I do not favor it.
I would also add a comma before "although".
Ultimately, (A) is eliminated while (B) is chosen because "a sum of" can be safely deleted, as (B) does.
(B) More concise than (A) by deleting "a sum of".
(C) "As many people in cold climates" means that Europeans serve in the capacity "as many people in cold climates".
Example: As an on-site doctor, Tom works in a famous ski resort and earns 900 euros per day.
(D) "cost a lot of money" is not as short as "be expensive". Shorter is better.
Besides, "a lot of" might be considered too informal / rudimentary in a graduate-level sentence.
(E) See (C).