I dunno, I've bought more vitamins recently than painkillers. It's common to take a daily multivitamin, few people take daily painkillers[1]. The vitamin industry makes plenty of money; dietary supplements are big business. Not that painkillers aren't, but there's nothing superior about a painkiller in an economic sense. There are whole stores devoted to dietary supplements, the most popular painkillers are illegal (heroin, opium, etc.).

Some links for the size of the vitamin market vs. painkiller markets:

The largest vitamin company makes $80 million a year in profit: http://www.foodnavigator.com/Financial-Industry/US-vitamin-s...

The total spent on painkillers in the US is $11 per person, which comes out to about $330 million gross, which probably means less than $80 million total profit: http://www.euromonitor.com/Specialist_products_to_revive_ana...

[1] Except aspirin, which is being taken for its blood-thinning effect rather than its analgesic qualities.