The sad fact is that if you want a new, authentic handbag, you most likely won't be able to get it at a "decent price" unless you find it on sale at a department store or REPUTABLE website, such as
Neiman Marcus, eLuxury,
NET-A-PORTER, etc. I don't know all the sites that you mentioned but a few of them are known to sell fakes. There are many sellers on eBay who sell authentic merchandise, but you have to be very, very careful. Those who sell authentic merchandise on eBay are either selling from their personal collections or perhaps for friends and family. For example, you cannot get Louis Vuitton at a discount -- their bags do not go one sale and are never sold anywhere except eLuxury and other high end department stores. Any webiste that tells you otherwise is lying.
You will learn a great deal here by reading the threads and you will be pointed in the right direction. Have fun and good luck!