Flutterby™! : adult sized erector sets

Meuon's picks look like they'd be more fun, but if, like me, you're having to build erector set type things on an adult scale, FlexLink looks like they primarily do production lines, but they have a US division and catalog (I'm not a fan of their web strategy), and Meuon found Macron Dynamics, which has the MacFrame set of parts, and a series of linear actuators. What most amazes me is that it looks like a 3 meter 40x40mm structural bar is about $65, which isn't the order of magnitude difference I expected from what I've paid for slotted angle iron for various projects.