The ECO versions of the Thon racks/cases use plastic instead of plywood/laminate, but they are still strong and rigid. This material also has the advantage that the whole case is noticeably lighter, which is nice when you have filled it up with heavy gear. The edges and corners are metal and the two 'doors' fit onto the body firmly and securely.
The snap-locks are clearly a cheaper alternative to the butterfly clasps and work fine, but they are slightly annoying when handling the case without the doors as they tend to flap around and get in the way, especially when standing the case vertically, like you would do when mounting some equipment in the rack. However, compared to the non-ECO flight-cases, this minor annoyance might easily be justifiable given the price saving.
All in all, a good cheap alternative that is robust and will stand the test of time.