I think the point you miss is yes you can rebuild one for that, but that is when you already have one, if you don't and you are buying one for whatever reason outright then considering it is effectively new I'd pay more, so someone faced with sourcing a engine for a project with nothing to start with a effectively new bullet proof short motor has got to be worth that imo, esp if with alt starter ps pump etc etc.
But with money the way it is at the mo, who knows, even selling anything these days is a challenge!!
tabetha