Al:
No idea on used price . . . whatever they could be worth to you. Correct, they've been out of business for quite a few years.
Personal experience with the Topline crankset: Put 57,000 miles on Toplines on our Co-Mo tandem and no problems at all; sold the tandem and it's still in use.
Just our experience.
Pedal on TWOgether!
Rudy and Kay/zonatandem