I don't agree when folks say most non-hunting packs can't handle big loads. It's too broad a statement. Most hunting packs can't either. Non-hunting packs cover a very broad range of activities. So it's important you do your homework to know which ones are meant for the task. The key is to go with quality brands and know what it was designed for. A good large volume mountaineering pack will hold up to anything you can comfortably carry. Your legs will fail before it does. On avg a person doing a multi-day mountaineering expedition will carry more weight than 99% of the backcountry hunters. The nature of what they do means a lot of gear, cold weather clothes and equipment. Frankly the mountaineering industry was way ahead of the hunting industry when it comes to packs.
That said, do your homework and make sure you get one designed for the task. There's a lot of mediocre packs out there (in both industries). You can save some $$ buying used or catching a good year end sale. Pack technology doesn't change that much. But generally the cost of a good mountaineering pack is similar to the cost of a good hunting pack. You might find more deals for non-hunting packs simply because it's a bigger market.
I use an older, high end Northface pack. Internal frame. Back when their brand stood for quality. It was $450 new and I got it for less than $200 at their outlet. Solid pack. Carried many deer and a few elk out with it. Every year I think about upgrading and go look at the latest designs of hunting packs. There just isn't enough of a difference to justify the cost. Slightly lighter fabrics, nice camo print, but that's really about it so far.
Weigh your options and if cost is a factor then there's lots of things you can do to save money.