[Rodney]

i charge $15/$18 regularly, am i to decrease for retail?

Do you mean decrease for selling wholesale to the mall shop owner?

Yes, when selling wholesale to a store that is going to sell retail to end customers, you will need to descrease the price.

Here are some threads that might help:
http://www.t-shirtforums.com/showthread.php?t=4780&highlight=wholesale+pricing

http://www.t-shirtforums.com/showthread.php?t=3855&highlight=wholesale+pricing

http://www.t-shirtforums.com/showthread.php?t=2381&highlight=wholesale+pricing