That seems like a lot for first run. Sure the cost comes down with quantity but what if most of those don't sell for one reason or another. Lets say you sell 1/3 of those shirts. 400 shirts that don't sell is a lot of money wasted. If you print up 50 (or even less) of each design, your cost of the product per item will be higher but your overall risk is less. You may not make as much profit to start but you will see which of the designs if any are sellers without having a lot of money invested.