Depends on what you're doing. I've worked on systems where we had 72gb and 96gb of RAM, and we tuned them within an inch of their lives.

But hey, 512k is good enough for anyone, Bill Gates once said.

edit: If I was doing something memory-intensive or performance-intensive, I wouldn't be on Heroku anyway.

I'd assume its for worker dynos with a process which cant easily scale horizontally.

I'm running a game server in node.js where the app's state is persistent so can't really so can't really spin up more dynos. The whole server lives in that particular instance.

I'm not that familiar with dynos but I can see how people would need even more than 2.5gb for specific jobs. We push the limits of servers with 512gb of RAM regularly.