The only thing I would say is that most supplements on the cheaper end of the spectrum would aren't anywhere as good in terms of protein content as those better established, big label brands like ON, as you mentioned. This is because many often use fillers so if the protein (of whey or any specific protein blend) is anything under 20g per scoop, it's a no-go, as fillers will probably have been used. Furthermore, I don't remember this too well, but I remember reading, a trusted article, that brands can mislabel the protein content per serving, for example in a 24g serving of protein only 19g may be used effectively for the repair of muscular tissue that you want, so I'd recommend staying away from the proteins that market themselves as being extraordinarily cheap and ones that have little to no reputation.
So what can you do?
If, for you, like me, budget is an issue then there are many ways in which you are able to attain protein sources cheaply. I'll convert the dosage, and how much of each item you would need to equate to a single scoop of whey or any general protein powder.
5 EGG WHITES - 25g of protein - highly inexpensive and protein from eggs has THE highest biological value of any protein, meaning it absorbs the best.
1 CAN of DRAINED TUNA - value branded tins are not expensive at all, a small can providing you with 24g of very high quality natural protein. Dave Draper, a monolithic 70's bodybuilder, highly advocated this as a protein source! Calorically they are very similar to a scoop of protein powder, 130kcal for a drained tin in brine, and 200-230kcal fir a drained can os tuna in sunflower oil (which I would recommend as the healthy fats offer a whole host of benefits for your joints and brain)
1 TUB COTTAGE CHEESE - These are literally 65p in Tesco (Value range) and for just 250-300 kcal can offer you a whopping 35g of protein per serving! fun fact WHEY (which is engineered to make high-end whey proteins) IS A BI-PRODUCT FROM THE PRODUCTION OF CHEESE, namely this one! But do add fruits because the taste gets a bit boring after a while!
-I hope that helps and good luck, I'm sorry I couldn't offer you the answer that you were looking for, but if it's quality of protein that you want, and you haven't got a stupendous amount of money to spend on it, mother nature is a far better alternative to less well known companies, who may cut corners in the production to keep their prices competative! Remember, it's a business after all!
Good luck,
-Nigel