You can use the freed-up engineer time to write better code which you can also keep for the life of the system though, though. It is not too hard to think of things which you could do in a few hours that would pay for RAM upgrades in perpetuity, even at BCC's relatively small scale. (Say, an A/B test which resulted in a 1% lift on my AdWords landing pages.)
It's precisely BCC's small scale that makes spending engineering time on performance optimizations expensive. At Google's scale it's worth several thousand engineers' time.
Really, you just have to weight the cost of the upgrades against what that time is worth. A week of engineer time is cheap compared to upgrades if your code runs on hundreds of thousands of machines.
