Anyone who plays NBA leagues on DraftStreet knows that fair value in salary cap leagues will have you paying about $500 per fantasy point. Some refer to this as "2x"... If a guy costs $10,000 and he gets you 20 fantasy points then he got you "2x" and you're on pace for 200. But, the multiplication ends here. From here on out it is all addition when looking for value. Some people look to get 2.5x because then they are on pace for 250 fantasy points, which is usually a winning score, but this isn't the stock market. You can't just buy one player and collect a return on that investment. You need to buy exactly 8 players and make the most of a $100k budget. This is why you need to tweak your equation; instead of 2.5x, you need to look for 2x+y, and I'd say y = 5. Then you're on pace for 240. Maybe you want to make y = 7 and shoot for 256, it's all the same.
Let me illustrate my point. Many people would agree that Jeremy Lin was the best value pick of this season on Monday when he scored 34 fpts for a price of about $3,500. They look at this as a "10x" return. I look at it as 2x+27. Since you need to get production out of 7 other players, I view this pick as a +27 pick. You're much more likely on pace for 227(2x+27) than 1,000(10x). Would you rather get 25 fpts from a $5k guy or 80 fpts from a $20k guy? 5x vs 4x... but 2x+15 vs 2x+40. Without question I take the 80 fpts for $20k.
It's tougher to get a high percentage return on the most expensive players compared to some bargain value picks on any given night. But, since you need to make the best use of your $100k budget, you will need to take some expensive players.