[robryan]

As long as it can reasonably expected to be mostly bug free and support everything you need it to with little changes to the app. It wouldn't need to require to much time playing around with it before the EC2 savings are eaten up by the wage costs of spending time on it. (Depending on how many servers you are running of course)

[nirvdrum]

This isn't a theoretical argument. I actually did this and it didn't take all that long and some of it was even fun. An added benefit is my specs run faster, too. So developer time is saved on every spec run now. You also hit that intangible of improved developer happiness.

Additionally, the X time exceeds Y cost argument really only works when people are optimally efficient. Clearly those of us posting HN comments have holes in our schedules that might be able to be filled with something else.