You said you were designing 50 ( which I assume is 50 different designs)
OK, You say 30 minutes tops, I still say it will you 2 hours each ( that's based on 35 years in this industry) You take the brief, you find the font, you play with the typography, you get approval, you check your ink saturations, convert to CMYK and do some colour corrections. Then you create each jpeg as pdf or tiff or whatever file format the t-shirt printer wants. You supply an individual laser copy to make sure the printer doesn't print your Grandmas birthday pixs. You instruct the printer or the client where on the T-shirt the image goes- it could be placed in the middle, which means if it's a large it could be protruding just above the waistbelt. You burn 50 indivual CDs and artwork. And you still have enough time to boil an egg in your 30 minutes?
Can I live in your world, cause my working environment oesn't run as nice as yours!
If you can do these in 30 minutes to an acceptable standard, show me the resuts, show me a profit and send me C.V. cause I may have an opening for someone like you.