I calculated my hardware breakeven, not too encouraging at more than 10 000 days
That's about 28 years, which is overly pessimistic IMO. While these profit calculators are helpful, they have artificial assumptions built into them about price and difficulty, both of which change in an unpredictable way. The prospects for making profit through mining certainly look dim right now, and I don't recommend starting now, but it is possible that price and/or difficulty could change in a way that makes mining more profitable. There was a brief period of time when you could pay off your rig in a month or two of mining, but those days are probably gone for good. But if you have access to cheap/free electricity, I don't think it's totally insane to hope you can pay off your rig in a year or two. Even with the precipitous drop in bitcoin price, I'm on track to pay off my rig in about 8 months (I started around the end of June). But I did a pretty good job of keeping costs down, and I don't pay for electric. For reference, I'm mining at 1200 Mh/s with four 5850s (bought for $150 each). I have them undervolted to 0.95 VDC, so I'm only pulling 450 watts from the wall, and running the whole rig with a 775 watt Thermaltake toughpower PSU that I got for $70. Homemade open air case. The whole rig cost me about $850. Of course price or difficulty could change in a way to shorten or lengthen that 8 month time frame.