What exactly are your projected online turnover figures? I'd be mightly impressed if it was 80,000 shirts a year. I think many here would be absolutley delighted with that turnover. With the right sort of eBay set up, the vast majority of people can make a lot more money through eBay than an online store.
Certain areas are difficult to crack. Joke text based tees is one, the eBay market being so flooded, and I think Dick will agree, with his eBay sales being, i remember, good but in no way sensational. For those areas, traffic manipulation is probably the best option.
But almost every major brand has an eBay presense, or is in the process of constructing a store (often for end of stock and seconds, where there is often the most profit to me made). Occassionally even it's done through a false "Mom and Pop" front.
Recently I worked for a company doing just this. I met with one of the crack teams eBay sends out, and worked with them for quite a while. They have sent teams to almost every major brand there is, from Apple to Sony to Target, and many of the umbrella companies to often control industries, such as Otto, one of the biggest clothing retailers in the world. Many even have an eBay representative stationed in the company.
I'm not sure you realise how powerful, and a money mine, eBay is.