I looked at some of your inventory. Very pricey engines - probably fair (not my point). Is it really a huge deal to go to 10 cents an item? $680 is probably the profit from a not so expensive offering. I don't think that's way out of line. I don't know what you meant by losing traffic due to eBay store promotion. Is this something that used to be free and is not available or a feature you have to pay "more" for now? Or is it just impossible to get the same promotional help you were getting?
You should have no trouble getting a site up and building a great site around your parts. Design will be costly - since I shop at used car parts websites - and the features that are "packed" into a good auomotive supply site must be a designer's dream! (or nightmare)
You'll start off with a lot less hits than you're getting today, but should be able to build on this quickly with good
SEO, directory listings and links. 6000 hits a day is "mad optimism" 10,000 well...you're at the right forum for
SEO but it's going to be uphill all the way - I noticed your domain isn't listed in Google - so I'd try to work eBay (as best you can) - while developing the new site IMO. Good luck!