I'm kind of with you on the yacht thing especially with the pricier ones (not sure you've looked hard enough for bargains, tired-looking but seaworthy 22-26 footers can be had for less than 10 grand, or so ive been told by someone who lives on one) but you lost me at the 70k number.
Not because it's too high or too low but because it's just so arbitrary. 70k in Glasgow is a very comfortable income, 70k in Tacoma Washington is just about enough to get by. In San Francisco there are indigents living (primarily) on the street whose income and benefits technically sum higher than 70k. And if any not-yet-indigent tried to move to San Francisco on that income they would soon join them.
I've always felt a scaling factor proportional to the extremes of individual difference makes the most sense here. Ideally the highest earning income possible in an economy should be somewhat proportional to the scale of capability in any given individual within it. I could acknowledge that people exist who might be five, possibly even 10 times as productive as I am when all of their merits are considered.
But there's no way in hell someone is 100 times, or 1,000 times or 10,000 times more productive or valuable and contributor to the world as me (or anyone), at least on the scale of individual capability. Without , that is, the benefit of some amplification apparatus that they happen to have at their disposal.
But it's pretty hopeless to get upset about these things. As a species we've hit some sort of ceiling long ago on efficiently allocating resources and rewards to ability. For example we'd much rather pay 30 bucks a week to give ourselves permission to dream about becoming millionaires, and as a reward watch yet another schlub (who like all that have come before him will do nothing of any consequence with the windfall) collect a two billion dollar paycheck - of our money - instead.