I'll give you my 2 cents on these:
1. probably not ebay. Much better to own your own domain name and real estate rather than just work ebay. Also, margins are low on ebay, on a proper ecom site, in most cases, you can get a lot more for the same products. Something about not having 50 other stores selling the same thing side by side keeps prices lower on ebay
2. for a small niche ecom site, you could probably do pretty well with $167/mo. if you know how to get a good return for your spend.
If you have any other ebiz questions, feel free to PM me... I owe you
