The numbers that never get considered enough are hardware wear and tear: a gaming PC pushed to its limits for mining burns through GPU batteries, memory, and power supplies way faster than it would just gaming, and replacing those components costs a lot. Even if you managed to mine something (which is hard without dedicated equipment), you'd have electricity costs, the depreciation of physical damage to your machine, and the hassle of managing it all for gains that probably don't top out at more than a few cents a month. If you want the experience of how it technically works, that's one thing, but don't expect to make any money back: you're going straight into the red.