From the feedback I've been getting via this forum and beyond it seems clear that, especially with respect to the situation in the USA, much depends on:
• where you're located
• how many and what sorts of pharmaceutical outlets are available (including legitimate/reliable online outlets)
• what types of insurance plan are in place

In Canada the variability is far less obvious. And down the pike, if and when the healthcare system gets its act together, pan-provincial/-territorial group buying may even the playing field even more and make Rx drugs much less expensive.