That doesn't help much to know that, I think Babette? T.m.h.o. it depends on what you have to pay extra! E.g. new price € 2299, trade-in price S975 is € 900, then you have to pay € 1399 extra. If the new price is € 1999, you pay 'only' € 1099. In the latter case, you may receive less for your keyboard to trade in. In other words, it can be a difference of two/three hundred bucks per case. Mostly you have to pay more if you have something to trade in (more risk for the salesman?). It is better to sale it privately. And the dealers are not happy to trade in a PSR …
But maybe there are other members who have trade in and will tell you …?