A couple thoughts...
If a brew method (non-espresso) that allows a fine grind is being used, for example a paper filter, then blade grinders can be perfectly adequate - the grinder just has to be run long enough to get everything to a good fine consistency. Blade grinders (I call 'em weed-whackers) are poor choices for coarser brew methods such as press pot because the beans that get ground at the beginning of the grind cycle get chopped up more and are too fine, while the beans that get chopped up last are too coarse; the uneveness of the particle extraction will be less than ideal; the too-fine particles will lead to over-extraction which produces bitterness, while the too-coarse particles will be under-extracted. But, use a paper filter and run the grinder long enough that all the particles are fine/teeny, and you're good to go.
In the arena of burr grinders, the sub-$90 options, aren't much better than blade grinders. I've seen plenty of people plunk down $50 on a Cuisinart, but the burrs are small, flat, and still produce a random-size of particles; while they're a step up from a blade grinder, they are still poorly suited to give one the uniformly sized particles, which in turn gives poor extraction.
The answer is the lower end grinders utilizing a conical burr. As much as there is a noticeable difference between a blade grinder and a low-end burr grinder, there is an even more discernible difference between a low-end burr and a conical burr.
I usually try to convey the idea to my customers along these lines; you're spending good money and trying to source the best beans you can, so why not spend the extra money on something like an Encore? Take the price of a lb. of my coffee, and you're only spending about 4lbs. worth to step up to a grinder that will enhance every cup of coffee. The grinder is not the place to get cheap and cut corners. I'll also emphasize the idea of amortizing the price over time; if the Encore costs $120 and it lasts 10 years (which it will) then it cost you $12/year or $1/month. Why spend $24/month on coffee, but not one more dollar to make that coffee the best it can be.