There are good eBayer sellers and, well, BAD eBay sellers.
I've recently started selling on eBay and everywhere I've read says that the customer is always right. I always accept a return withing 14 days. I normally do not refund shipping, but if I was asked and the customer was very upset I would because it is more important to me to keep a customer happy.
Here's my advice: In general, always start with the seller, but you've done that and are not happy. The seller seemed rude to me and I can't believe he responded that way! So, file a dispute with eBay. I noticed you did this, so I'm not sure if you are in the middle of it or if you have resolved it. Continue with eBay as far as you can - either until you are satisfied or until you can't go any further. Have you left feedback yet? Feedback is the best way to know if you are dealing with a reliable seller (or buyer). It is also the way you can make sure others know about your problems. You should leave a negative score and briefly describe what happened.
All in all, it sounds to me like you found a bad seller. I haven't had any problems (yet - fingers crossed) in buying or selling. So I hope everyone doesn't cross eBay off their lists! There are a lot of good sellers!
I hope you get this resolved and can get the machine you want