I don't know that they're much lighter than Cherry MX Blue, if it all, but have you tried Kailh Box whites? There are at least a few sub $50 boards on Amazon with them. They have slightly less overall travel than MX blue, much crisper/consistent tactility, yet have an almost entirely imperceptible bump to overcome on the downstroke, a smaller bump maybe than even MX blue, but certainly a much more pleasant one.
It reminds me a little bit of capacitive buckling spring, but only in the fact that the tactility is basically little more than a hint, yet it still manages to feel and sound good. It doesn't have nearly the same overall feel, or that pingy model F magic, but they're certainly interesting switches.
I just compared it against some Cherry MX blues. My perception tells me that they are lighter, although they seem to be rated the same as the blues. I think that may only be because of the lighter tactility of the box whites, but that may also be all you're looking for.