Heya Dennis. This is just my opinion but,
Nope, the glass is cracked and not worth $500.
Why would anyone want to pay $500 for a piece of broken glass that you would have to take the risk of working on it just to use it and it still be a broken cylinder in a restored pump?
Even if someone has the tools and the experience to pull off a correct grinding down of a cracked glass cylinder, the odds are HEAVY that it will break further during the processs.
I would consider saying to him, "since you want the cylinder, I will buy the pump for $500 less and you can sell the glass by itself", or something to that effect.
,,,that is my perspective on a broken/cracked/dinged/holed out cly and I'm sure it is not shared by all but to me, broken glass is broken glass and can't be "repaired" once damaged and therefore not worth anywhere close to what a undamaged or new piece would be.
Good luck on your Hunt!
...Later today...
My apologies for the bits of repetition with what Kevin posted above. He hit the post button while I was still writing my thoughts down.
He is dead on with what he said and also Richard and Steve too!