I might be able to help in a small way - I got made redundant and had to cut my expensive Butternut Box dog food out of my budget completely, amongst other things.
I started bulk prepping and freezing my dog’s food and my monthly bill went down from £70 a month to £20 and I still do it now I’ve found another job as he is thriving on it. I’ve got a smallish dog so bigger dogs might be more costly to feed, but you’d still save a decent amount of money if your usual dog food is already costly.
I try and get all the meat and veg in the reduced section so it is usually cheaper than the £20 a month that factors in full-price food.
my shopping list is from Tesco and my dog is 10kg and gets 250g of food split over breakfast & dinner:
4 x 500g pork mince £10
1x frozen broccoli £1.10
2 x bags of carrots £1.40
2x bags of sweet potato £2.40
2x red peppers £1.40
1x tin of sweetcorn £0.60
1x tin of green lentils £0.50
1x bag of frozen peas £1
1x bag of spinach £1.20
i make it in 4 batches on a Sunday (2 in slow cooker and 2 in wok) and I freeze it in these large sectioned trays (think an ice cube tray each with 4x 250ml sections).
I know this method is still maybe more than you’re looking to pay, but it’s mega healthy and it’ll fill your dogs up longer than cheaper dried food which in my experience can sometimes cost more as you need to buy more of it to fill the dog up - and as a result I spend less on supplementary treats as my dog isn’t mooching around for food.
This is where it potentially gets a bit mad, because during this time, I ate the same food as the dog - exact same ingredients as above but I would add seasoning and spices. I would use a ‘cube’ of the food as a dinner with a baked potato, pasta, rice or in a wrap. Again, this takes time but I made the food for a whole month (albeit just for one adult and one dog) over the course of two days. This method left me and the dog full when I had no money coming in. It’s boring as hell cooking it and eating it and you’ll be in the kitchen for 2 full days, but for me, it was worth it.