Alright, I'll give this my rough estimates:
$50 - Piece of garbage probably made in India.
$350 - Nice older saddle made in England , Germany, or France (Crosby, Stubben, Beval etc) with plain flaps. Padded flaps are very popular nowadays and many people prefer them for jumping. If you have a good strong seat, you'll be fine jumping 2'6" in a plain flap.
$800-1000 - Modern padded flap saddles made in England, France, Germany, and some
Argentina (Pessoa) or Australia (Bates).
$1500-2500 - Top of the Line Hermes, Butet, Delgrange, Antares, Luc Childeric, etc etc.
NEW: Basically double all prices listed above.
Of course, you can always find used saddles at all prices between what I have listed. Especially if you go with the not-so-famous brands. For example, while a Crosby Prix des Nations may run around $300, a Crump Prix de Saute may only be about $200. They almost exactly the same saddle, both made in England, it's just Crosby is a more desired brand name. Or, a Harry Dabbs Original A/O may save you a few bucks over a Pessoa A/O (Dabbs designed both saddles and they're almost identical). But remember, if you ever decide to sell your saddle, you wouldn't be able to sell it for as much.
And remember, the best saddle to buy is the one that fits your horse!!