10x is a ballpark figure, the actual number depends greatly on the specific code. The ‘meatier’ the function calls you make, the faster it is, since most of the time is spent in the interop layer. Calling a bunch of tiny functions in a tight loop (like a bunch of math nodes) is going to be much worse than calling meaty functions like traces / collision queries.
RE: Determining what functions correspond to nodes, 4.2 includes a ‘go to definition’ feature in the right click menu for nodes, but you can also copy a node and paste into Notepad to inspect it in 4.1 or earlier, see this post for details.
Cheers,
Michael Noland