Instructions
Start up a game of "Fallout 3" and open the console by pressing the ~ key.
Type the following code into the console and press enter to set your Barter skill to maximum, thus setting prices to a minimum.
modpcs Barter 100
Enter the codes 000630F3 and 000388F3 to get an extra boost to your Barter skill, hence lowering all prices still further.
Input the code 00031DB8 to get the "Master Trader" perk, which gives you a 25 percent discount from all traders in the game.
Enter the code 0006F592 to get a 10 percent discount from all the traders in Rivet City, and 00030FEB to get a 30 percent discount from Craterside Supply.
Go to Tenpenny Tower and hack the terminal next to the bar on the first floor. Activate the 50 percent VIP Discount and the 10 percent Holiday Discount to get everything on the menu much cheaper.