I'll throw in my 2 cents too. I've purchased one Dyson brand new for $300ish. It worked amazingly and probably still does. I do not have it anymore. No bag is great, emptying is simple and fast (and IMO not messy at all), filter changes are very easy and the filter is washable and reusable. The few times I've had clogs (from sucking up long skinny things), access ports are really easy to get to and its fixed in a minute or two.
I now have another one that my father in law picked up at good will for some absurdly low price ($50 maybe?). It also works great and I have no complaints.
Is it overpriced? It is more expensive than other vacuums, and less expensive than still others. Does it do its job really well and make my life easier? Yes. Am I willing to pay money for a quality product that lasts a long time and makes my life easier? Yes. So, overpriced is really a mind set. Are there other products that cost less and provide the same quality and service life? Probably!