For some reason, Sainsbury's are advertising them as 25p but they're actually 6p when they're scanned in. It's not an error on their side, they've been selling it for 6p for ages.
I've always used Heinz but this stuff isn't that bad actually. A lot thicker than Heinz and it tastes a lot "fresher".
My local store finally got them back in stock after about a month, so if you do happen to come across them, be quick!