Its 70g more efficient in terms of HP pots not bought. However, if it costs you 1 failed kill during a gank, or 1 death from not being able to run away, that's costing you at *LEAST* 300g in death gold, not to mention time wasted.

And then there's the fact that since the boots start is faster, camps are respawning earlier, and thus, you're farming faster overall, there's another gold increase from the boots start, albeit a somewhat intangible one.
On the other hand, having to run back early or being caught with low life at the end of a clear could just as easily get you killed.

*SOMEONE* is doing it wrong if you're never seeing successful lvl 4 ganks. And a successful gank can be as minor as simply blowing flash with minimal cost to your laner, allowing him to be more aggressive knowing his opponent simply can't commit as strongly anymore.

Also, not only should lvl 4 ganks be common, but lvl 2 and 3 ganks should be popping up on some junglers, such as Shaco, Lee Sin, Jarvan, and possibly Alistar. Hell, Skarner is one of the junglers who can do the wolves>blue>their red>gank path really well.
Yeah, i usualy do quite successfull level 2 ganks on Shyvana, and back when i was learning the game my level 3 Udyr ganks also went pretty well.