I'd say that by spending money on elections, both as donations and as taxes, we do buy a good: good governance (preferably) and peaceful transfer of power.
The problem is that the market is not efficient: only 2-3 offers, mostly from the same two brands, each brand with its own known serious problems. The process is actually an auction of sorts (first past the post), and returns are not accepted!
IMHO, the cost is the least of the problems here.