It doesn't - prices I've seen are more like $200 US for the base level Philips air purifier in a retail store, and there are brands with even cheaper offerings.

It doesn't - prices I've seen are more like $200 US for the base level Philips air purifier in a retail store, and there are brands with even cheaper offerings. I see one on Amazon for $135 USD. Of course, that's still not $30, especially when you add in the cost of replacement filters, but it's much better than the $400 quoted.