So you are willing to invest thousands of dollars into your hobby
Yes, near $3000 (2400 EURO) per three years, and that equipment will work three or five years more, without additional charges. So it is like near 500 EURO per year for 10 PCs, before they all burn.
but you can't afford Corona for a bunch of hundreds of euros?
Thousand of euros. I will need three Corona licenes for all PCs, 1350 EURO with box versions (for year or two, before next Corona upgrade), or 900 EURO per year.
You can just buy one seat. Since it's your hobby, i am not really sure why you need to DR on 10 computers at once. I would understand it in commercial environment, where you have some clients with requests and some deadlines, but since you say it's a hobby, then there should not be much of a need for such extremes as rendering on 10 computers at once.
Agreed. But when my render-farm will be ready, I will able to search for some work in that direction (I hope so :) ) With one seat it is simple money waste, if you have little farm at home. There are other renders, that can be used on render-farm, and they will be much faster on 10 PCs, than Corona on one (or three) seats.
Electricity bills of those computers rendering for a bunch of days each month would probably easily grow over the price of SaaS licence.
$2-3 per render day, 24 hours of render.