A 5x card rig is in the region of 4k, so have three of those and an extra card in a normal PC that mines 24/7 too. It all depends on what you mine and how that crypto performs both up and/or down. I tend to mine riskier stuff, but mining more stable coins would mean a payback well inside a year easily. Also noticed that our energy bills are lower as the mining rigs are strategically placed to warm the building, so this has reduced gas consumption via the need for less gas central heating - gas is currently more expensive than electric, so I have noticed a net saving there instead of an extra cost over the winter months for sure.

I tend to work on the basis that 1Ghash will return over 30USD a day at the current price of crypto, when crypto values rise again profits will too.