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The Blast Mastery for Fallout: New Vegas is worth 15 G

You will get this through normal game play as long as you are using Energy weapons (e.g Plasma Rifle, Laser Gun and so forth). Also if you have companions with you it will hinder the damage count some. For every HP of damage they do that is less towards your damage. Which I think is a fair trade off since you get the XP for everything they kill.
You can also find the Tesla-Beaton prototype. It's located exactly south of the Matthews Animal Husbandry Farm in a crater where a plane has crashed. Consumes about 45 electron charge packs per shot and does around 135 dmg depending on your energy weapons skill, but to get it you have to fight through some sentry bots and mister gutsy bots as well.

You can keep track of this by going into your PipBoy under Data - Misc - Then press Y to bring up the Challenges press X once to go to next Challenge type then Scroll down and find Blaster Master.