True but it was much cheaper when a computer you might have on for other reasons wouldn't consume noticeably more power for your donation, eg computer lab admins which I think made up some of the top contenders of the leader boards. There were definitely groups that would run clusters of computers just for the donation (my dad was one of those too, there was no other reason to run those PCs other than Seti@Home) but for the average home user it was spare cycles that were low cost to free.