whats a slant 6 worth ?

Yeah, with the oversized valves, new seats etc I have about $800 just in the head in my motor. Lots more than I thought I would in a " truck motor" if I hadn't bought the carbide burrs I did, just to do the work that I did to it before the machine shop even saw it/ and spent the 15 or so hours making cast iron dust within the head myself (vs letting them do it for me, they just touched it up and finished it for me, then magnaflux'ed it for me) and if a generous member here hadn't given up a few hours on his Saturday afternoon/ spending that time with me and my engine's head on his flow bench, I'm sure I'd have been at least in the same range as you, for dollars spent on this head ...
I see super six stacks with asking prices of $200 and going way up from there, when people can't give away whole engines sometimes..... Is also crazy. At least as crazy as spending $1500 on just a head.

I have never had anything of mine on a Dyno so I'm gonna have to go by the butt Dyno/ from memory of all the V8 powered trucks like my current one I've owned a over the years/ but my goal is to have built a /6, that runs like it has the power somewhere between what a new 318 or 360 "of the day" that would have come in these trucks, back when they were new.
Hope that makes sense