Electricity costs money

Not $400 a month, it doesn't. At least not around here (we average $0.12/kWh and I don't personally run my cards over 300W.)

And there's a lot of labour and effort involved...

Theoretically, the people who hang around HN are more likely than most to be capable of the labour and effort of setting these things up and maintaining them.

People don't even run their own email servers...

People don't run their own email servers because a convenient coalition of spammers, standards bodies, and large email providers have done their best to make running one's own email server almost impossible.