$500 is too expensive for me to bite on. I started with the gpd xd for $150 and backed the gpd win for $330. That over 100% in price jump was pretty high especially when PS4, XBO and switch are lower. If they can get the price near $350 than I might bite but it's getting too pricey for me.
I agree $500 is too much for a handheld game console or even game console in general.
It only makes sense if you can fit it in your life as a tablet / laptop replacement as well. If you look at laptop prices, it won't be a high price.
If you want to just game on it, you are right $500 is alot. If you can work on it whatever your job is and replace carrying a huge laptop every day AND game on it, it is cheap.