A cheap dehydrator will do just fine! At least, as long as it can dry at low enough temperatures. The only problem with cheap is that it may not last as long, but hopefully by the time it dies you'll know whether or not an investment in an expensive one will be worth it to you.
However, the blender deal is very different, I think. I'm not sure it's the wattage that makes the difference, but rather the rpm's and possibly the design.
I made perfectly fine green smoothies in my $35 Hamilton beach blender for months. So you simply don't have to do any different.
But what you get from the Vitamix (and presumably the other, too) is texture. Smooth, velvety, creamy stuff, without little identifiable bits and pieces. It's absolutely not essential, but for the long haul, for me it's indispensable. I completely agree with you that just munching on carrots and apples and celery sticks could get boring in the long run (though ask Sim: she's now swung back to that end of the spectrum, I think!).
So things that give you a variety in texture, like the spiralizer (probably the very best value for $25 you'll ever find) and the Vitamix and a dehydrator, and even a food processor, make a huge difference in feeling satisfied without our old comfort foods.
So if you're wavering, absolutely start small and inexpensive and see how it goes. Then when you want to get a more expensive version of whatever it is, your motivation will be very high and you'll find the money much more easily!