I bought Bissell Bagless powerforce turbo from Walmart a few months ago, for about $60-70. This model has the HEPA filter, but there is another one the same w/o HEPA for $40-50. My theory was that even if I had to replace it every 2-3 years, I'd still be spending way less than a Dyson at $300-500. Previously, I had a bag vacuum, and I'd have to use a new bag every 1-2 times, because of two dogs. Talk about expensive!
With the bagless, I empty it into a trash bag (or even just a plastic grocery bag) outside, and then tie it up, so any dust that might fly up doesn't land in the house. All the filters are washable, so I wash them often to prolong their life and keep it running well. Takes a few extra minutes, but saves money, and makes me feel like the vacuum is almost new again each time.