If price remains that high for a plastic Trezor, for sure it will never reach the main stream.
The price isn't that high for something that will keep your bitcoins, I guess when you have a very small amount you don't see the value. Plus this is one of the first of it's kind, so you kinda paying to make history.
Let´s compare it to the FIAT world:
You own 1000$ - no need for a tresor just put them in your wallet
You own 500000$ - can´t put them in your wallet because it won´t fit  

 Would you buy an ultra safe tresor for 200$ to protect this amount?
You won´t get one for 200$ that is safe enough to protect that amount of money.
I admit there's no other hw device with comparable functionality.
And you have to admit you can secure your BTC for free:
Huge BTC amounts I'd simply put into an armory offline wallet (old laptop).
Small amounts on my mobile, medium amounts on my laptop. Backups for each.
So tell me why should I spend so much for a plastic Trezor - sorry, but I simply do not see any advantage than 'it's new' and collectors may pay 1.x BTC in the future.