For stock engine the gain is so minimal that it is not worth the cost (not enough piston clearance). For a larger engine then the gains start to work well and you can get more midrange and or top end power. I sell them for $700 exchanged. You'll also need heavy duty springs which we can also provide.
I can get a variety of thickness of gaskets and you can go a little thinner. Pair of gaskets should be under $100 with shipping. BUT, a lot of effort will be involved. Not terrible but nothing that's a few hour deal.
Stock is approx .032". We usually use .027" on the normal builds. BUT, I can get them thinner. I want to say as thin as .015". You could get a single OEM gasket and use the outer layers (one layer for each head) and discard the center layer. Never done that personally but I know that's an old trick.