It would not be worth it to me, but the parts do add up to that pricing range.
The add on piston kits aren't rocket science. Piston in place of gas tube. Fit and align accordingly. Test fire and adjust as necessary.
You are going to lose, probably, .5MOA over the same gun in a gas system for follow up shots and your multiple shot/hit sight picture will be slightly more compromised.
But, if you absolutely HAVE to have a piston driven AR, he is not out of normal pricing given the package he has there.