Something akin to one of those online travel sites that finds the lowest price. Before you could purchase however, the doctor would have to let them know you have a valid prescription, and there would be a need for safeguards to prevent fraud.
Good question, Sonny. The simple answer is the medical lobby, which pumps millions into Washington won't allow it.
If there was a real free(capitalist)system, the Govt. wouldn't care less how much you paid for Doctor prescribed drugs.
The way it is now, is because of the powerful medical lobby making you pay thru the nose.
Regards