A lot of stores are relying on the "hassle factor" to stop you from being persistent . Same idea with the "mail in rebate". Too much hassle for many busy people to bother with mail-in rebates.
How did you make out? I sold 2 $500 Lowes gift cards on eBay. I live in the US. They seem to sell at a 10% discount to face value. I got about $450 for ea. Seems to be a lot of gift cards for sale there.