Diana, you should come up with an hourly rate for your time, since you already seem to have accounted for your materials. The $1.50 covers the stones or the stones AND the transfer tape for each design? How long did it take you to create the design, make the transfers and press the transfers? Those are the things that you need to get paid for now. If you don't want to do it on an hourly rate, you can do something simple like determine how much profit you think you earned for that job. Let's say you want to make a 50% profit for everything you do. Then your 1.50x4x150% would recover your total costs of $6.00 and give you a $3.00 profit for that job.
What to charge if customer supplied shirt? 
