I just bought a refurb 256 for ~$350 out the door ($319 sticker) so I imagine you could get a bite in the high, mid-200’s although you’d probably also be cross-shopped against the 64 GB refurb (that’s mostly out of stock though)
On the used market you'll be up against 64gb models upgraded with 1TB SSDs, which are a lot better value compared to the 256 or 512 versions from Valve. So look what those cost and subtract around $100, as that's what the SSD costs.