On the subject of price, I think a person first has to come to grips with how they want to assemble a hifi system. I keep learning that it's best to buy on the basis of audition--a piece of equipment is good value if it sounds better, by my criteria, than the competition and if it is of sufficient quality to satisfy my musical expectations. Is a particular, used sample of the Rotel RP-855 as good or better than a new P2? Unless I had an opportunity to audition it next to the Rega, I have no way of knowing. I would rather spend $650 on something I know I like than risk a fraction of that on something I haven't heard.
Another thing to consider is whether a 'table meets your expectations. $650 isn't much to pay if it will make you happy for the next decade or two. On the other hand, it could be money wasted if you really need P5 or P9 performance to satisfy you. When I sold my Valhalla-equipped LP12 towards a new 1993 model with the Cirkus ugrades, I downgraded to the Basik power supply, intending to add the Lingo at a later date. What I found was that the Cirkus LP12/Basik/Ittok LVIII easily met my expectations, and I'm still using it in that form. Yes I can hear that the Lingo is better, that the Ekos arm is better, and that the Keel takes it to another level again, but I don't need them to enjoy my records--I'm at a point of satisfaction. Before buying a P2, I would want to audition not only the competition at that price point, but models at higher performance levels to see if that's the level of playback that is going to satisfy me long term. Even if not, I might still buy a P2 if the dealer has a reasonably painless upgrade policy.
I have to admit to a bias against used turntables. Maybe I'm too paranoid, but taking my LP12 as an example, its sound is too easy to compromise by failing to keep the bearing well filled with Linn's own oil, by transporting the 'table without supporting the inner platter to keep the spindle off the thrust plate, by mounting a cartridge without first removing the arm, by overtightening the screws that hold the armboard in place, etc., etc. I might buy used from a dealer I trust who backs up the product with a warranty, but even then, parts do wear out, and buying new might still be the most cost-effective when you consider how long it will provide optimal performance versus something that's already logged many thousands of hours of playing time.