Oh, for the comparatively sane salaries of American sports!

The NFL gives out big contracts but rarely means it — most of the money is not guaranteed and often is not paid out.

The NBA spends enormous sums on players but 1) the league has a salary cap, which taxes big-spending clubs and 2) its big money goes to demonstrated superstars.

Major League Baseball gives nice bonuses to high draft picks, but nobody makes serious money until a player has reached free-agent status.

In world soccer, particularly European soccer, clubs are doing crazy things all the time, and sometimes the stacks of money go to players who are 20 or 21 and have not actually done much of anything yet.

Like Barcelona’s new addition Ousmane Dembele.

I make no claim to deep knowledge of the Euro soccer scene, particularly when stepping outside of the English Premier League.

Which may explain why I had no idea who this Ousmane Dembele was, a 20-year-old guy Barcelona pried away from the German side Borussia Dortmund … at a cost of about $145 million — which could buy entire leagues, a generation ago.

(He is French, of African heritage, and he is a striker who also creates goals for teammates. Or has in his limited history.)

Second-highest “transfer fee” in the history of soccer, trailing the $250 million or so that Paris Saint-Germain gave to Barcelona for the Brazilian forward Neymar. Which was more than double the previous high for a world soccer transfer fee, given to Paul Pogba all of a year ago.

Madness, no doubt, but Neymar, still only 25, at least has done stuff. He has become Brazil’s best player by a wide margin. Won things with Barcelona, like a Champions League and a couple of Spanish league championships.

Dembele has one season with Rennes, a middling French club; he scored 12 goals in 26 matches. Then he was sent to Dortmund, one of Germany’s best clubs (once we concede Bayern Munich are in a different league); he scored six goals in 32 league matches.

And now he goes to Barcelona? For the second-biggest transfer fee in the history of soccer? At age 20? Even the player has seemed a bit taken aback by this. He keeps talking about how young he is …

I searched for the words “Dembele signing Barcelona madness” and got half a million results. Perhaps the most significant was a story in which FIFPro, the international players union, called the signing “transfer market madness”.

That’s a step into nuttiness American sports teams have not yet contemplated.

Why? Because a player at 20 … it’s not a sure thing he is going to be a star, never mind a superstar. Six goals in 32 league matches with Dortmund? That’s enough to get Barcelona to send $145 million to Dortmund?

Let’s concede Barcelona knows more about this than I do, but how much of this buy is a trying to save face after losing Neymar to Paris?

So, we must say this about U.S. sports: At least no one gets enormous money until they have been in the big leagues for four or five years, and shows us what they can do. Which seems downright sane, compared to what goes on at the top of the Euro heap.