Well, the price is still cheap as some joints are more expensive then 5 usd.

Dude, it's 5 dollars per joint. If you want to have a full body of joint textures it costs 100 dollars.

I think the prices are fine, for 100$ + 30$ (for full 512) you have all the customization options you'll ever need.

That is, if the joint textures can also act as a force/relax color (in other words, if the texture isn't affected by the force/relax color).