I've never seen the point to a fancy blender. If a low priced one blends it as well (it just takes a few seconds longer?), doesn't the smoothie taste the same? Thrift shops like Goodwill often have a wall of donated blenders where you could get one for like $4.
Typically the issue is that, in my experience at least, most cheap blenders will never do what a good blender can, at least when it comes to trickier items like ice, nuts/grains, or fibrous greens like kale. I've had a few cheap blenders (mostly hand-me-downs or yard sale finds) and they've all had issues with consistency unless I was blending something that was already pretty smooth to begin with. I'm not sure if the difference is due to motor power, design, or some combination of factors - but there's definitely a difference.
A blender is just like any other tool - the quality of their construction will affect their performance and longevity. Typically higher quality construction comes with a higher price tag, although (as we all know) not ALL high price tags mean better quality. But a really cheap blender will generally have more limited motor power, less thoughtful design (meaning more difficult blending and harder to clean), and cheaper plastic components that are prone to breaking and snapping with regular use. If you use a tool often enough, there's something to be said for investing in decent quality.
The Ninja seems to get pretty good reviews for a blender that I'd call moderate price range (a step up from a $40 Oster, but not the investment of a Vitamix). It's also worth looking on Craigslist if you know what you want, I see nicer blenders up there from time to time. Cuisinart has some OK reviews and I regularly see them on Craigslist from people who have upgraded to a Vitamix.
As an aside, this is the bad boy I've been using to blend up my smoothies: http://www.etsy.com/listing/120428628/vintage-retro-iona-blender-ionablend
40+ year old Iona model, inherited from a grandparent. The fact that the motor is still kicking is fairly impressive, unfortunately it doesn't blend greens worth a damn.