Don't worry mate, most merchants take the p when they get a chance, if you don't check the price of everything before handing your cash over they'll sting you, £2.60 a metre is sharp, £1.9 ish around here. but buy in bulk when I'm loaded and see offers.
I can go into one of mine, a builders merchant, buy something one day, and it'll be a different price the next day, depends who serves you and what mood they're in, bloke off the street sometimes gets it cheaper than me!!! . I only use them occasionally for that reason, my regular plumbing merchant is great and worth the extra half hour trip in the morning, I can ask for stuff without saying "how much!" steady discounts too.
Vote with your feet mate! If you can, not everywhere has a choice