First of all - I am basing all of this on an assumption. You are not doing this purely as a hobby and the goal is to start, sustain, and build a profitable side venture. This will be something you see yourself enjoying but as importantly - will produce some return on your time and money investment.
So here it goes. You are fighting simple economics. As a buyer of items and as a seller of items (especially obscure ones) you want the most efficient marketplace. As a buyer - competition keeps the costs down. As a seller - you have a market for what would surely be difficult to sell and have many bidders competing for the item(s).
As an entrepreneur you want to focus on things:
1) You know a lot about (some would argue that you should have very in depth "domain knowledge" about all areas of the business.
2) Your "domain knowledge" is a large (or the largest) barrier to entry (for example practicing law or medicine)
3) You are offering an obvious advantage to your consumers and are able to communicate that advantage to your target audience
4) You are deeply passionate about and might even continue doing this even if it continues to cost you more money then you make
With all 4 of these things you have a small chance of producing a return on your investment and building a worthwhile business.
I would guess you don't really have any of these things and are looking to make an easy buck. Your money, time, and energy would probably be better spent reviewing your investments, fixing up your house, or in other activities much more certain to bring a return on your investment then this.
As I see it:
1) You don't know a lot about all areas of the auction business (that is why you are asking)
2) There are numerous free / low cost auction software packages that anyone and everyone can setup. There is no barrier to entry here.
3) There is no advantage to using your site and on the contrary - an item sold on your site would probably take MUCH longer and sell for MUCH less then on EBay - even factoring in the fees.
4) This is at best a passing idea / hobby to you.
Trust me - been running a business for almost 6 years and it is a major pain in the butt. I have probably made less money then if I had kept a normal job and have alienated friends, family, and others through the years. What I - and others who do this - seem to have in common is a passion for the "right answers" (different from being right), a love of people, and the stupidity to keep on going when everyone else has walked away.
Here is my recipe for success - at the risk of sounding preachy. Life is very short. Figure out what you do better then most everyone else. Figure out what you LOVE to do and would do that even if money wasn't there. Try to combine the 2 into a business or join a business that supports your admissions. Enjoy.
Take care and good luck. If I am wrong about your passion and you are willing to fight the juggernaught EBay - then my advice would be to team up with companies already with a foothold, find others who augment your domain knowledge, and build a business plan you can sell to investors as it would take a substantial amount of money and time to even make a small dent in EBay's business. This is how Google become a brand name when others were much more established in the Internet search market - they did something better then anyone else, built a strong following, and managed growth and opportunities successfully.
