I've ordered from Johnson bags twice in the past two years. 2 years ago they had a 15,000 minimum but you would receive 16,000 from the manufacturer. Last year they were able to reduce the minimum to 10,000 but you will receive 12,000 from the manufacturer. They use the +/- 20% rule. The printing plates also ran $200-$250 for each color but of course these can be used over and over again. Make sure your design is perfect so you don't have to re-make plates if you change your design down the road. Also, most bags like these are made in China and companies in the US are sourcing out the work.
They do a great job but just be prepared to spend around $2500 on your first order.