What is the threshold of the ratio of units sold(T-Shirts) over the profit loss incurred when one 'outsources' the various sections of the job versus the do it yourself approach?

• creating one's own ready image
• performing one's own Transfer Paper Printing
• executing the Heat Transfers to the BLANKs

Including in the equation what weight should that ratio be given when put in contention against the flexibility of doing it all in house, namely having the ability to do great batteries of tests to iron out details(no pun here) in order to surmount unforeseen obstacles that would take an unwieldy number of cycles to resolve due to distance when outsourcing(i.e.: not being in an in-house communication setting)?

Granted, if the prototyping is easy and straightforward, surely the question is answered. But if not, as I believe my case is... is it a given?... only outsource if the designs are generic and cause no concerns?

To help you help me, I can tell you that my designs are close to 100% ready, yet I foresee they still are moving targets and subjects to unknowns! I just simply do not have the experience to be able to look at a piece of art and decide upfront where I might encounter problems at what stage in the chain of processes.