Eh, that heavily depends on language and dataset you're working with. I've seen "simple" data with some fat thing like RoR on top of it having 10x the latency of the underlying database after all the ORMing.
Most of my experience with this actually comes from RoR. I worked on one so where rendering slowed everything down to a grind, but more often than not it was making Yu noptimized queries, too many queries, inefficient calls to other services. I used to work as a consultant, so this was true for quite a few apps. However, I also usually was the person most interested in relational databases and my view might have selection bias.
I have a similar experience. Also, for the longest time Rails was also incredibly slow at generating JSON, of all things. JBuilder [1] was a few orders of magnitude slower than using .to_json directly or other libraries.
