except power bills and cost of hardware
"oh hey, thanks for the ten dollar donation! wait stuff, it's 1 dollar now. now it's 20"
1. My computer is always running anyway. It costs less to mine, with speakers/moniter turned off, than with an idle CPU/GPU and a moniter turned on.
2. You can hold your coins until they are more valuable.
3. It's kinda hard for the whole market to instanly crash, as it's a peer-to-peer regulated service.