I paid $165 for mine, NIB with 2 mags, holster, lanyard, cleaning rod and multi-tool less than 5 years ago. Around here I'd be doing very, very well to get $200 - 225 for the whole shebang. YMMV, as supply and demand set what the market will bear.
Personally, I'd have to want a Makarov real badly to pay that $300 since there are so many other choices on the used market in that price and size range with better features and chambered for more powerful cartridges.