I'm not sure how "wholesale" their prices are but check out VistaPrint:
VistaPrint is more than likely not a viable option for OP, they charge WAY too much for "bulk" pricing.
I'd suggest you check out Alibaba, although you'll need to find a seller that won't completely screw you over after you finally make a massive order (it's happened before!).
I'm in the t-shirt business. PM me and I can help you out. I would avoid vistaprint or any place that is mostly digital printing...digital prints suck compared to screen printing. I have made a living competing against the likes of customink, because I'm smaller and my prices are lower.