But then if you do sell it, you might not be able to get the same performance back without spending even more money.

I am in the same situation. Could have earned 50% profit if I sold mine

I got Vega just after its release so I could try it out. My main gaming setup later got 1080Ti in it so it doesn't really affect me if I sell it... in a similar situation, I've also thought about about selling the 1070 in my VR system, and return to using my older 980Ti. In practice, the only difference is power consumption and for gaming it doesn't matter.

Probably not being able to say "I own Vega" is the biggest loss for you

And everyone will call me nvidia fanboy... I still have 3 RX580s mining

People also call be an Intel fanboy when I say I spent 7 years on Intel CPUs and even today.... Even though I'm like 'screw you Intel not buying your copy-and-paste quad core parts again' and stick with my 2600k for all this time

I had a 2600k for 5 years before replacing it with my current 6700k, which is about 2.5 years old now... and for gaming faster than my Ryzen CPUs.