Bonnon, I don't understand where you get your numbers from?
We usually have 4 TT sets and one MT set (We only had 3 this month, because at some other time we only had 2 in one month instead of 4, so actually one less in total). That makes 17 Fairy Coins a month to get them all according to my calculation and most people don't even aim to get them all (At least I see "I don't like the colors/items" posts in announcements all the time. Not everyone likes and wants all items)
I would gladly make less Treasure Trove set. It's a lot of work and puts me under much pressure each month. Unfortuntely in order for this to work, someone needs to come up with an awesome idea how else we could make up for the missing income, as we are not making enough money to cover KOfK's costs most of the time and couldn't be further from our goal to obtain extra funds to pay for advertisement or even hire people to help out.
I am not making Treasure Trove sets for fun - This site's existance relies on them heavily.