I think you're asking for way too much money for a start-up, and I don't see how you can possibly expect to be in business for this upcoming holiday season.
You need to do a set of financial projections that show various milestones as you grow, indicating how much capital you need at each milestone to move on to the next.
If you are still in the concept stage, then you are probably looking for money just to build the infrastructure to get started. Then you'll look for dollars to start marketing and actually generate revenue (proof of concept). Then you'll look for dollars to grow what you've started. And so on.
You're not getting $4.5 million on Day One. And if you were, you'd be giving up 90+% of the company, as it's highly unlikely (oh, let's just call it impossible) that your valuation will be anywhere near, let alone higher than, $5 million.
I'll be candid...I don't get this business. It's a discount eBay for luxury items? You don't think eBay couldn't just come in and pound you into oblivion? And do you really think that there are that many people willing to sell high priced items online? And buy them? Who buys something for $10,000 online sight unseen? I know it happens, but enough to make a business out of?
Also, if you get 1,000 transactions at $20 each, that's $20,000 in revenue, not profit.