He paid less than $600 for that gun. Gunbroker prices are not representational and never have been. Note how the vast majority of those auctions close without a winning bid. [edit, I just checked Gunbroker. There were 30 PT1911 auctions that closed within the last 48 hours. Typical asking prices varied, but none were above $700. Most were between $500 and $600. Total auctions that closed with a winning bid: 0. That's right, not a one sold. Which means the market value for a used PT1911 is less then ~$550 right now. Gunbroker is a joke - until they introduce posting fees, people will continue to post at inflated prices - because it doesn't cost anything if it doesn't sell.]
That gun is now used, fired, finger fucked, and just basically has passed out the front door of the retail shop. It's not NIB. And he's asking for a ~20% markup above what it cost him to get it.
I would pass. You could counter $475, which IMHO is what it's worth considering it's non-new state. But he won't take it and may even hold a grudge. Just pass.