You're right why not 0.001 btc if powerful gpus are out of reach? Of course 1080ti would be great because as difficulty rises it will be used for many years and profitable as well. I think 1050ti can be

This is what I'm planning by the way. I have an i3 first gen with 4 gb ram and 450 watt psu which is not 80+ My gpu is so old it's beyond earning anything so when I come across a powerful but cheap gpu