The cost of owning a glider is reasonable, even if you own an expensive glider, as long as you choose one that doesn’t loose much value and you keep it in good shape.
The cost of operating a glider is the main factor (although not nearly as bad as power plane): tows, aero retrieves, membership fees, oxygen, tie down fees, gas for driving to the airport etc all adds up to much more than owning a glider, especially if you fly as often as you should.
Just as the saying about buying a house, buy as much glider as you can comfortably afford.
I often see folks who can effort buying a nice glider, but instead trying to spend as little as possible and end up hardly flying as a result.

Ramy