Total comp for a new-grad Googler who doesn't negotiate at all will be 110K base +18K bonus + 25K stock annually = ~153. That's without negotiating at all. Negotiation can push that across 200K annually in extreme cases. From that perspective, its not as gargantuan a leap. And similarly, I expect that this person was able to negotiate their google offer, so it would be higher than the "default" for an L4.
I edited it to 60% to account for negotiations (assumed +10-15k annually), but I didn't think there was that much room at the new grad level. I remember Google being very inflexible on base, and didn't think you could get 200k annually with just negotiating (which would involve tripling the initial stock grant you listed, assuming that base is inflexible).
Even still, are the bands truly that wide across L3 and L4? I suppose I'm most astonished that the median L3 and top of L4 are that wide apart. Thank you for all the information.
And as to your second question: a rule of thumb that I think exists is that total comp approximately doubles every 2 levels, so you get a ~40% increase per level on the median. Keep in mind that a new grad offer is not the median of L3, but the bottom.
Google, for example, offered a base salary just over 100k. Is the difference between level 3 and 4 (what I assume 2 years of experience gets you) really ~60%? The annual RSU difference is also drastic, as OPs offer was 100k in stock annually.
Note: I'm calculating the 60% by looking at annual salary + stock + target bonus each year.