I rarely buy boxes of Whiskas or Felix anymore because my cats are so fussy they disregard certain flavours and I end up throwing lots of food away. I tend to buy the odd individual sachet of those brands in flavours that I know Bernard will eat - even though this appears more expensive it's probably more cost effective for me and certainly less wasteful. My 2 females mainly eat science plan dry food (which I am assured by my vet provides excellent nutrition) but they will also eat the odd sachet of applaws or some of the individual 'gourmet' tins or sachets priced at up to 85p for a single portion. The females like tinned tuna as an occasional treat - not sure if tuna is a female thing because my late Tabitha also loved it and would come running from wherever she was in the house if she heard the sound of a tin opener, whereas my male cat doesn't like it at all.
I do spend a lot on cat food but I like to give my cats what they like and what I know they will probably eat. I would hope that the more expensive foods provide a higher nutritional quality and contain what they say on the label - but I may be fooling myself and succumbing to clever marketing in pet stores. I agree that in the case of pets it probably doesn't matter too much if the products contain horse meat as long as the meat is still nutritional. I'm lucky in that I haven't eaten meat since I was a teenager so I've not being eating horse meat myself, it's been a good time to be a vegetarian.