I had a REAL toy Yamaha synth voice sampler, a VSS-30:
http://www.sonicstate.com/synth_reviews/yamaha_vss-30.cfm http://www.harmony-central.com/Synth/Data/Yamaha/VSS-30-01.html My kids banged away on this puppy for years and years. It still works great! What a fun toy (especially changing your voice and having each key play the "voice" in a different tone -- has built in mike). I paid ~$35 for it on close out when it was discontinued.
I bring this up because of this whole "built like a toy" issue with the 2000. In fact one of the keys on the VSS did break a while back. When I opened it I too was surprised to see all the keys were "cut" from a single sheet of plastic (a single mold for all keys on a single sheet is more accurate). They key "fingers" on the sheet (the note keys) bend using the pivot point of the plastic. So the flexibility of the plastic is what provides the action of the keys. Clever! Cheap!
The danger is not from overuse of the keys causing the plastic to fracture at the "pivot point". In my case one of the kids pulled UP on that key (maybe it got caught in something) and that's how it broke.
Anyway, surprisingly, I was able to glue that "key" back on the main sheet of plastic and it again played good as new. The action in that key is not materially different from the others.
You want Steinway Action? Go pay Steinway prices! I don't expect these keys to "break off" from overuse. But don't pull UP on any of them (this will happen when you move the 2000 and something gets caught (a sleeve on your jacket?) UNDER one of the keys)....
Cheers,
Bob