Educational discounts tremendously help. Revalver MKII is 50% off if you are a student. Cubase Studio 4 cost me $199, and Steinberg let's you use it for commercial purposes even.
Also there are so many good free plugins out there (the free amp sims are fantastic these days). I'm a firm believer that mixing skill far is more important than expensive hardware or plugs. That being said, there are a few things that are almost necessary. Decent monitors, a decent audio interface, and a decent computer which can all be had for the price of the price of a new amp head. Also, if you can make good sounding mixes from minimal equipment, imagine how great your mixes will sound when you can actually afford all the high-class stuff.