One reason discussing those numbers is hard is the variable compensation section: RSUs.
An E4/L4 (the level right below senior) easily makes 400k right now depending on which company they joined. Their typical offer was 160k base and let's day 82k RSU (325k over 4y).
With the usual (~15% of base) bonus, that's 160 * 1.15+82=266.
But now let's assume they joined 2 years ago, so they got refresher of stocks that are roughly 20k per year extra (80k vesting over 4y), 266+20+20=306k.
Here's the catch though, the 82k/y from the in-hire grant are now worth 160k/y: it's {stock price today} * 1/4 * 325k / {stock price at join date} , and look at FB, GOOG, AMZN etc trajectories.
Same for the refresher, the oldest one is probably worth around 40k/y, and most recent one probably worth 30k/y,
So this year exact TC could be (bumping base with 2 usual raises to 170):
170 * 1.15+160+40+30 = 425k.
That's ignoring extra (~10% of base) for on-call compensation.
That E4 doesn't need promo to E5. The math can be repeated for E3 or E5, the higher the stock number was, the higher the effect.
That's the effect of stock compensation and alignment of employee compensation with company performance. Of course if those share prices go down, so does the TC. There's a company in FAANG known for their frugality famous for not offering refresh "because the stock price is doing so well", but even without the refresher, someone's initial stock award from 2-3 years ago is worth a lot more today.
Some companies are starting bad trend these days due to them offering only 1 year vesting stock awards, instead of typical 4 years (smaller on-hire awards but bigger refresh), where an employee cannot benefit from the compounding effect of stock growth anymore. The employee can "hodl" their vested shares, but the vested shares are usually less, since ~1/3 is removed to pay for the tax the vesting represented.