I don't think it is a waste since I don't just buy figures just for the sake of buying.
I think about whether I like it and does it have investment value (e.g. Sideshow Exclusive, Hot Toys, etc...) before I buy.
When I am sick of a figure, I usually can sell it for a lot more than I paid or break even worst case scenario. For example, I have sold Hot Toys Hicks, Takara Casshern, and numerous Sideshow Exclusives for a lot more than I paid.
Trust me, it is a better investment than buying cars, electronics, dvd's, cd's, or video games.