Most garbage collected languages can't handle all the memory available on modern systems. Hardware costs pale in comparison to revenue and the cost of programmers. (Unless your service is free)
In general if your server is making you money, you'll make more money improving the service than reducing the amount of RAM the service takes to run.
In summary, test the conversion rate of a page/feature/etc, not how much RAM it uses. If you're going to performance optimize, attach a profiler and take the easy wins, don't spend too much time on it unless it's a ridiculous amount of resources or your margins on razor thin.
"Hardware costs pale in comparison to revenue and the cost of programmers."
That's not a law of physics. The number of servers you need depends on the number of users you have. The functionality you have to build usually doesn't. So the more users you have, the less true your statement becomes.
"Most garbage collected languages can't handle all the memory available on modern systems."
I don't think that has anything to do with the languages. I think that has everything to do with the quality of the memory manager implementation, and there is at least one memory manager that does deliver in this respect, namely C4.
In general if your server is making you money, you'll make more money improving the service than reducing the amount of RAM the service takes to run.
In summary, test the conversion rate of a page/feature/etc, not how much RAM it uses. If you're going to performance optimize, attach a profiler and take the easy wins, don't spend too much time on it unless it's a ridiculous amount of resources or your margins on razor thin.