Print shops offer discount prices to qualified customers. These discounts are known as "contract pricing." Basically, print shops like it when they only have to print the goods and not spend time or money sourcing blanks, quoting prices or fixing artwork. So they give discounts in those cases.
Yes, sourcing your blanks would be providing your own blank clothing.
PO = Purchase Order. Printers that offer contract pricing will provide a detailed price list. This way you can submit a detailed purchase order - and understand exactly what the job will cost - without needing a quote from the print shop.
The common range for contract screen printing is $0.50-5.00 per print (not including the shirt), depending on number of shirts and number of colors. Also, screens cost $20 per color as a fixed setup cost.
The common range for contract digital printing is $2.00-7.00 per print (not including the shirt), depending on the number of shirts.
Those ranges are pretty wide, but that's because it's impossible to give an accurate price without knowing the volume of shirts you need. And just to explain the reason for this... A very common issue in the print world is when a customer asks for a price quote on 200 shirts; then comes back and says they only need 20 shirts to start out but still expects the price to be the same. Then they get mad when the price goes up due to the lower volume. Then the printer gets mad because the customer is upset. And the whole relationship blows up before it ever gets started. So the bottom line is, if you want to get accurate info from the print shop, be prepared to give them accurate info for what you need. It's a mutual respect thing.