You likley won't. As stated you will pay a premium finding one in stock. I was wrong on the $540 price, that one has the ambidextrious safety (which I don't like) here's the retail price direct from LMT for the SOPMOD stock and 2 stage trigger and lower
http://www.lewismachine.net/product.php?p=27&cid=4&session=dc0d8ed0b8d0dbb0adea44afd24fca6c
but again they are way behind on orders and some dealers are adding a premium for in stock status.

Here's a great deal, Denny is a good guy.
http://global-tactical.com/lmtdefender2000withsopmodand2stagetriggerinstock.aspx