I buy them from my local pharmacy, they don't really vary in price more than a couple of cents. I don't use them often, only if I've been eating weird things and want to see if they are having an effect. Usually I go by how I feel.

netrition.com

I think Walmart may have the lowest price. I don't get mine there, because the store is too far away. I buy them at a discount department store near my home. (It's a locally owned chain that, I think, is limited to the pacific northwest.)

I use them twice a day, first thing when I get up in the morning and last thing before I go to bed at night.

In the UK they do vary in price from over £9.00 to around £5.00 just by walking down the shoping center and checking the price in each. 50 in each pot but it's easy to be ripped off if you don't check the prices.

ebay most definatly