Mine are getting through a large bag a week. (Either Pets@Home or The Range, about 3kg)
I've seen bags in local Petshop, but they are smaller. Supermarket, very small and expensive. Don't know how long it's been there. I've thought about finding a stable yard and trying to buy a bale, but it's a pain to transport and I'm a bit with horsehay, there can be big sharp pieces in it.
Farmways Online does 4kg bags (IIRC £4.99 or £5.99 + p&p) but I can buy several and keep in the garage.
I found the "Devon Meadow Hay" from the Range was pretty good value and consistently good quality. Unfortunately, there isn't a branch in Scotland, so I have to load up on it when visiting the inlaws across the border.
In the past, I have bulk ordered hay and that's worked well, but you do need secure, dry storage space (mice like hay, too!) I use a bit more fleece and less hay now than I used to, but still give the boars "general" hay as they like tunnelling and chewing, but also supplement with Timothy Hay, specifically for eating. I sort of get it anywhere I can find it cheap.
I'd be interested to hear where others manage to find hay bargains!
I buy mine from Notcutts pet centre, but that's partly because I'm a bit of a gardening nut so have their 'Sage' discount card and get 10% off everything They had a 6 bags for price of 5 deal on at the weekend so I stocked up - but we don't have a huge amount of space so I couldn't really stockpile any more than this.
50p bags from local pet shop. No idea exactly what it is in it. One bag this time of year lasts 2-3 weeks for 2 pigs. They much prefer fresh grass on the lawn, which is all they have in summer, (but obviously all grazed down this time of year) and 3rd piggy won't eat hay at all, he gobbles barley straw instead.
I've bought that Devon Meadow Hay before as its really cheap in my pet shop (but I am in Devon!) I also bought a huge bag of dried grass from there too. Somehow my guinea pigs have got mites from one of them so they are proving to be not too cheap in the long run what with mite medicine. They are living indoors so the vet said it must have been one of the bags that they came from.
I am lucky to have friends who have a farm and regularly bale up hay so I am currently working my way through a bag of that at the moment.
Mine have always had the same as the horses, they lived in the stable with her for a few years but now they're at home I just bring a bale home either form the yard or the local farm which at the moment is cheaper.
The buns live in a shed in the garden (there are 6 of them so lots of space needed!) and I've got one of those plastic storage trunks against the outside like this only I think mine was about £15 from Focus before they went out of business.
The two old girls are getting on for 7 now and they've had horse hay all their lives with no problems.