This month with Walgreens I haven't been quite as on top of things as I should have been - and I'm loosing about $10 because of it.
The first was choosing the wrong acid controller tablets. I got the 30 pack instead of the 25 pack. $6.99 + tax down the drain. I had a $10 off of $40 purchase coupon, so it wasn't lost money, just money I didn't earn.
My other error cost minimal out of pocket but will cost $4.99 in rebates. I used my $2 register reward coupon and my $3 off pert plus coupon, so I had less than a dollar in out of pocket expenses. But now I can't find my receipt to add it to my September claim.
Lesson learned: be VERY careful when shopping and ALWAYS know where your receipts are.