100-1000 USD depending on specifics
try customer service at browning.com
50-550 usd
500 USD
Allows for adjustment of barrel harmonics.
Try midwestgunworks.com
A call to Browning for a manual or a trip to a gunsmith is in order.
I just purchased (Dec 08) a used Browning A-Bolt Medallion with composite stock, BOSS, Browning fitted hard case and Tasco 3-24X scope, all in 98% condition, for $600.
This site will answer your question: http://www.browning.com/customerservice/qna/detail.asp?ID=107
@ 400 USD
Check w/ Browning, but I think you are correct- BOSS will interfere with iron sights.
You will have to shoot to find out.
BOSS stands for "Ballistic Optimizing Shooting System". With the BOSS system installed properly, the intent is that once a rifle is sighted in with a particular ammuntion, the BOSS increases accuracy by reducing barrel vibration. Each caliber, bullet weight, and Ammunition Manufacturer, has a setting for your model of rifle. The setting is what Browning calls "The Sweet Spot". For instance, you may have a .30-06 and you shoot Federal 165 grain bullets. The BOSS guide will tell you which setting on your BOSS (sweet spot) will optimize the shooting accuracy of your rifle. Click on the link to the Browning Web page that shows the settings for all calibers rifle models.