For the US we have PureBites which are wonderful!They're a cat/dog treat like Thrive and are just freeze dried meat,though during holidays some have vegetables and such as well so be careful which kind you get.They're very high quality,but as it is a natural product you will find pieces of fat in there as well but you can simply discard them.Most of it is meat though,so it isn't like you're getting ripped off or anything
Dog biscuits and general dog treats can be good,but make sure there are no unsafe ingredients.One example of this would be BHA/BHT/ethoxyquin which is unfortunately common in a lot of the big brand dog foods and treats such as Purina,Pedigree,etc.I know that Dollar General sell a safe cheaper dog biscuit,though I forget which dog size it is marketed towards though this is a great option for budget friendly treats.
Another tip for the US is that Marshalls/Home Goods and other similar discount type stores sell really nice dog treats which would be insanely expensive otherwise!
I'd also recommend Gerber baby puffs and freeze dried strawberries!Both of these can be fairly affordable as well,but if you want freeze dried strawberries you can get a good size bag of plain freeze dried strawberries from Target which are a much bigger bag and cheaper than what can be bought at a pet store.I find them delicious and so does my Syrian
Target also has a big range of freeze dried fruit,not sure if it is all plain and without any added sugar etc but I will check next time I go.