Transfers are, for the most part, like dating.
It's not enough that you like someone. No. Success depends on whether or not they like you, too.
Ultimately, it comes down to what you can offer each other. A boy might like a girl because she's attractive. She might like him because he's funny and, to her, that's important.
Somehow, some way, everything evens itself out.
A woman might not think her prospective mate is particularly good-looking, but decides he's rich enough to make up for it. The man might decide the woman isn't very intelligent but is so attractive that it doesn't matter.
Transfers follow a similar path.
Club A wants Player B because he scores a lot of goals and that's what they need. Player B might prefer to move somewhere else—somewhere near the beach, perhaps—but decides to join Club A anyway because they pay well and are based in a tax haven.
It's easy to see why Manchester United might be interested in Bayern Munich's Toni Kroos. He plays in midfield, among other things, and he's quite good at it. At least better than what they've got.
The Manchester Evening News are reporting that the German is David Moyes' top target this summer.
He can offer United goals and creation from midfield. And, still only 24, he can offer it for at least another eight years.
But what can United offer him?
By reportedly agreeing to pay Wayne Rooney £300k-a-week for the next five-and-a-half years, United proved they can still compete in an age of Oligarchs and Sheikhs.
The purists might not want to hear it, but players have a right to seek out the best financial package they can when they're moving clubs, and United have shown they can still offer competitive wages.
But Chelsea, Manchester City, Barcelona and Real Madrid can all offer similar deals, as well as the added incentive of Champions League football. It's looking increasingly likely that United may not, although they can offer regular first-team football.
The Champions League has become the gold standard competition in world football—ahead of the World Cup—and Kroos may not want to miss out, even for just a year.
And, like the less-attractive man pursuing a beauty queen, they might have to make up the difference in cash.
Bayern's honorary president, Franz Beckenbauer, already believes United will have to push the boat out to get their man.
You have to make a decision as a club when someone's demands are going through the roof.
There is not a single player who's worth changing your entire wage structure for.
Nobody's indispensable. If the player wants to stay at Bayern, I can only advise him not to overplay his hand.
United must also convince Kroos to leave his home country and the club at which he has grown up.
On top of that, Manchester might not be as desirable a place to live as Barcelona, Madrid, Paris or Monaco, but it's not St Petersburg or Donetsk.
And despite Sir Alex Ferguson's retirement and a difficult season under Moyes, United still have the aura of one of the biggest clubs in the world. They also have the history to match.
Whether those things are important to Kroos, only he will know.
When Moyes sits down to overhaul his squad this summer, his job will be made easier if he has Champions League football to offer his targets.
But, 11 points off fourth place with 11 games to go, it's far from guaranteed.
It means Moyes might have to rely on United's other plus points. And hope some of Europe's most in-demand footballers agree to a date.