the problem is going that far, and missing the migration in a fixed camp situation, which is likely what you would do on a budget hunt.
Getting there is the expensive part- NWT as an example, I had four changes of planes just to get to the camp. It took a full day (15 hours) and a half day to get there, same coming back.
You could use sky miles to buy part of your tickets, or you could drive if you have a decent mileage per gallon vehicle that will carry all your stuff.
Motel nights to and from, probably, are pretty expensive too...everything in Yellow Knife or places like that are more expensive because it costs a lot to get things that far north, just like remote places in Alaska, as an example.
Once you get to camp, the more you pay, generally, the more likely it is you are going to have the ability to get flown out in front of the herds in case they are not coming into your area.
I know if I go that far, I want to SEE caribou. I have heard many horror stories about Quebec..so do lots of research.
One other thing you should think about is joining one of those services like Huntin' Fool- they offer cancellation hunts. You could join for around 100 bucks, and save your money up, be patient....you know...maybe you wont go the first year..but these cancellation hunts come up everyyear where guys for one reason or another just cannot go so you can get them reasonable and do it with a reputable outfitter if you have done your homework.
I would decide where I wanted to go first, what price I could afford, and then do the cancellation hunt thing, or go to bowhunter banquets, SCI banquets, NWTF, whatever is in your area and try to buy a hunt at auction. Usually they are for two people...and you can contact the outfitter and make a deal for the other two guys you have in your group - nothing is written in stone with an outfitter, and getting four guys at once, well thats sometimes a plus for him so don't leave a stone unturned, don't be afraid to ask..you can only get told NO.