I just checked my pricing for the job you described and I would be at just about the same cost as you...about $11.60 if I had used transfers. But, if I quoted that job screenprinting I would have quoted between $13 and $14 because of the tie dye shirts. Depending on the size of the designs, you might have saved a little if you were able to gang the transfers on one sheet but at low quantities you don't usually save alot because the pricing is so expensive at the lower quantites. Ganging would mean you had to use the 12 sheet pricing.
This is the struggle I've had for a long time.....you just can't compete with direct screenprinting in most cases. However, somewhere on here I read something that made alot of sense and that is to not try to compete on price but on quality and delivery. Many transfer houses such as Transfer Express, Versatranz, etc. can turnaround transfers within days which allows you to offer quick turnaround times as a competitive advantage. However, I've started to see alot of screenrprint shops offering 7 days or less turnarounds.
I offer both services and basically use transfers for larger runs where my manual setup is less efficient. I can turnaround smaller jobs pretty quick and especially 1 color jobs. Or, if I am backed up with orders, I'll offer transfers and have somebody press them onto the shirts while I am busy screenprinting.