It took some patience and looking, but I found a great used leather child's saddle on ebay a couple of years ago for just under $100. I hadn't thought of looking on ebay until a rancher friend suggested it.
The only problem I can see about buying a saddle on ebay is you can't sit on it and find out how well it fits you nor how comfortable it is. Glad to hear that the other people have had good luck.
If there is a saddle shop nearby go check them out. Ours is always getting in used saddles on trade and they have a great selection.
Hope you find a great one.
I have a two year old handmade saddle for sale on a 16 inch Wade tree, rough out finish, stamped to a half breed with the Hamley stamp. Five inch horn, with a six inch cantle. This is a work saddle and it shows it. If you are interested I could send pictures.