Hey, just to help you out a little, the price of the Sentry (Vltor, not Magpul) at Tokyo Model Company is HKD1880. That's the price they listed last time I went there, which was about 2 weeks ago. The price is for the 10.5" model I think, I don't recall seeing any 14.5" Sentrys.
I didn't ask if they had any in stock though.