I would put it more like this…….
If you took the money you would pay someone like Speier to revamp them, to the point they were actually “better” enough to justify the effort/expense of doing it, and added that money to whatever you could sell them for……..you’d have enough(or very close to it) to buy new heads.
Edit- I guess it might come down to whether or not he’s got any interest in working on heads like this.
On his site he claims he will evaluate someone’s heads, and offer a plan for improvements……..for free.
You just pay the freight.