Certainly paying 20FC or so for an items seems very expensive. However, it is necessary to think if the item is very old or rare or elusive and deserves to pay this amount of FC.
Old knuffels are too very expensive in FC

In my opinion the problem to get old knuffels was only half solved.
Years ago it was impossible to get an old knuffel. So, not expensive, simply not available.
Now, it is possible to get practically anything but at very high prices.

I've been buying treasure trove items with some, now have a horde of 70 lava lamps, and have gotten two of the older knuffels I was missing. Still saving up for more of the older knuffels, and treasure trove sets as they come out. Not all of them, but for instance I want all colors of the Lord Wuffel set and two of the Arachne sets, so if I win any of your FCs they'll go to that.
And now you know what your FCs go towards when I get them. ^_^

edit: Oh wait you're selling some directly? May I purchase one of them? (Or a Lord Wuffel set in any color if you want to do it that way?)

No, the vast majority of them are from trades with Momo, when she still had a bunch of WK items she wanted and was giving out FCs for sets of 10 of them.
Then a couple from a monthly feeding contest (LeannaAnne's), a couple from Kyan's charity, some very kind folk selling (about four or five different people when posting various LTB threads), and the rest from getting lucky spotting 'buy now' FCs in the market (you as well as a few others)
It's been made slightly less frantic of a search because of wulfalice's wonderful help, too.

Hee hee, Firn really does do a marvelous job, yes!

Would you be willing to sell me a Lord Wuffel set (or a FC for it) for 35k?