I really agree with the others. Get a genuine article, you will not be sorry. I recall my very early days of backpacking, I bought a "looks like the real thing" pack and I loaded it up with all the gear I had and took off. It is a good thing I was young and dumb! I was able to manage the trip but I sure remember being miserable and the pack was very uncomfortable and not very sturdy. It pretty much was done after one trip.
I learn as I go, still learn all the time. One thing I learned from that first long pack trip was that just saving a few dollars was not worth the effort. I paid more than if I had bought a proper rucksack. I had to replace the pack after that trip and I was out the money for the first junky one also. A good pack can last many years, or even a lifetime. The important factors are, is is comfortable? Can it carry all the things you need? Does it fit? Fit and comfort are real important criteria. For instance, I do not fit the US Army ALICE pack, not even close. It pinches nerves in my back that make my legs go numb. I had to endure an ALICE for years in the army and would not recommend that pack to anyone over 5ft 10in tall, that seems to be about the tallest person it will fit properly.
If you can't afford a proper pack, save more money and wait, if possible. You will be glad you waited and got a proper, quailty pack. Just my recommendation. Cheers!