Which is more expensive, servers or developers? Which is more expensive, server or opportunity cost?
In a lot of cases, performance of the server isn't the determining variable in the overall cost calculation.
In addition, the relationships between those variables likely changes over time.
I'm guessing that for most startups, HR expenses and opportunity costs are pretty important relative to actual server performance.
Obviously, if the point of your startup is some kind of high-performance computing thing, the equation is tipped more towards server performance. But, you probably aren't using off-the-shelf frameworks in that case, either.
Not to beat a dead horse, but ask Twitter. I expect their answer would be something like "Migrating off a non-performant solution to Java was more expensive than just doing it right in the first place."
Also, my point was that the newer jvm frameworks aren't much more complex or time-consuming than Rails so developer cost isn't such an issue. That said, not much compares to Rails for getting stuff up and running quickly.
Cost is relative to the maturity of the business. They may not have had the funds or time to do things the right way the first time, and if they had tried, they might not have ever made it into near-unlimited-budget-land.
Fair enough, back then the newer, sleeker jvm frameworks may not have existed. But now, perhaps there's no such excuse.
Maybe these options will become really compelling once Kotlin is released. It compiles to both the jvm and JS so it will hit the performance, convenience and "fun to write" sweet spots all at once...or so I hope.
In a lot of cases, performance of the server isn't the determining variable in the overall cost calculation.
In addition, the relationships between those variables likely changes over time.
I'm guessing that for most startups, HR expenses and opportunity costs are pretty important relative to actual server performance.
Obviously, if the point of your startup is some kind of high-performance computing thing, the equation is tipped more towards server performance. But, you probably aren't using off-the-shelf frameworks in that case, either.