Taurus made a good point -- as your skill and experience increase, the size of the blade you need (or think you need) decreases.

To a certain extent, I would argue that's also true of the quality of the blade. A top-quality blade is superior in strength and sharpness, to be sure. But if you have worked with knives a lot, you have a sense of what kind of blade (even from the supermarket or dollar store or Sally Ann) will do a job, and how far you can push it.

For example: stainless kitchen knives are much more brittle than field knives, though they take a decent edge. They also tend to have a very thin tang, so they're weaker where the blade meets the handle. But kitchen knives can and do accomplish real work every day. You just don't use 'em as a prybar or machete. You adjust your technique to the blade in your hand. (And if you're wise you have something as a backup.)

The caveat of course is that the failure of a cheap blade, when being used hard, creates a real risk of injury. You really have to watch it.

Aside from that, it's actually a lot of fun (and a cheap hobby) to pick out cheap blades from second-hand stores and garage sales, and use them in the field. Or maybe that's just me :-)