[Bought] ≤10.1lb flywheel
 

For cheap. And I say 10.1lb because FT86 Speed Factory has the Spec aluminum flywheel listed as being 10.1 pounds, the lightest I've seen. I haven't actually dug too deep into lightweight flywheel research yet, but that is the lightest one I've noticed.

I'm not in too big of a hurry to get one, so I can wait for a good deal. I did just spontaneously purchase pulleys though, so now I am a bit more interested in investing in a flywheel than I was just last week.