Unfortunately, the leather saddles I would recommend aren't in that price range if they're in decent shape. I use a Wintec 500 in the winter (I can leave it in the tackroom without having to worry about mildew) that I like very much. It doesn't have an overly deep seat, the knee rolls are interchangeable/removable, and it's comfortable for both the horse and myself. You can get great deals on them on eBay. The only caution- I have one horse with a wide back, but very high withers. With the wide gullet installed the tree fits, but there isn't enough wither clearance. He's the only horse of many that I can't use it on.
Around here, they're perfectly acceptable for showing.