Hay is famous for its bookshops, of which there are many. Some are antiquarian, specialising in rare and first editions, some, such as Murder and Mayhem, specialise in particular subjects, others just sell second hand or new books. There is also at least one shop selling remaindered new books for £1 each.
One word of warning though - check your purchases carefully. I got a bit over-excited purchasing the odd book or fourteen, and when I got home found that one of my remaindered books was missing some pages.
What to buy: Books
What to pay: Anything from £1 to £lots.
There are actually some stores in Hay on Wye which don't sell books but other things. I found the stores in the craft centre very nice. My favourite one had all sorts of jewellery, in all price ranges. It was fun just to look around and even more fun to go back and buy some earrings.
Next to it there is a fudge store, where you can get a lot of different sorts of fudge and chocolade.