THOMAS: [reading a letter from Sabrina] ... I decided to be sensible the other day and tore up David's picture. Could you please airmail me some Scotch tape?
Why does Sabrina need Scotch tape mailed from America? Paris doesn't have any Scotch tape? Of course, the real Paris does have Scotch tape—but the Paris in Sabrina is fanciful, distant, and magical. It doesn't stock mundane office supplies.
SABRINA: Maybe you should go to Paris, Linus.
LINUS: To Paris?
SABRINA: It helped me a lot. Have you ever been there?
LINUS: [thinks] Oh, yes. Yes. Once. I was there for thirty-five minutes.
SABRINA: Thirty-five minutes?
LINUS: Changing planes. I was on my way to Iraq on an oil deal.
SABRINA: Oh, but Paris isn't for changing planes, it's... it's for changing your outlook, for... for throwing open the windows and letting in... letting in la vie en rose.
LINUS: [sadly] Paris is for lovers. Maybe that's why I stayed only thirty-five minutes.
Paris helped Sabrina—not by making her forget, but by teaching her how to seize life and love. Linus needs the same medicine. Though staying in Paris for thirty-five minutes obviously isn't enough to quite do the job.
LINUS: Oh, yes, the cold businessman behind his marble desk, way up in his executive suite. No emotions, just ice water in his veins and ticker tape coming from his heart. And yet... one day that same cold businessman, high up in a skyscraper, opens a window, steps out on a ledge... stands there for three hours wondering... if he should jump.
SABRINA: Because of her?
LINUS: No. No, that was another woman. Sabrina, do you find it hard to believe that someone might want to blot out everything for sentimental reasons?
SABRINA: Oh, I believe it! Do you know what I almost did for sentimental reasons? I... [stops herself]
SABRINA: I went to Paris to blot it out.
Sabrina tried to kill herself before going to Paris, though she's reluctant about saying so. Paris then becomes a kind of afterlife, or resurrection. It blots out the sad past, and introduces a glittering future. (Though, of course, in real life, you don't need to try to take your own life to get to Paris. You can just get on a plane.)
LINUS: Why're you looking at me that way?
SABRINA: All night long I've had the most terrible impulse to do something.
LINUS: Oh, never resist an impulse, Sabrina, especially if it's terrible.
SABRINA: I'm gonna do it.
SABRINA: [reaching out and turning down the brim of Linus' Homburg] There!
LINUS: What's that for?
SABRINA: We can't have you walking up and down the Champs Elysees looking like a tourist undertaker! Another thing, never a briefcase in Paris and never an umbrella. There's a law.
Going to Paris is not just going to Paris; it's becoming the sort of person who can be in Paris. That means that Linus, when in Paris, will no longer be a "tourist undertaker", but will instead turn into someone who wears his hat stylishly. And, of course, in seeing Linus as someone who could live in Paris, Sabrina sees him as someone romantic (or capable of romance at least.)
DAVID: Funniest thing. Linus Larrabee, the man who doesn't burn, doesn't scorch, doesn't melt... suddenly throws a twenty million dollar deal out the window. [stops at the door]
DAVID: Are you sure you don't want to go with her?
LINUS: Why should I want to go with her?
DAVID: Because you're in love with her.
If Linus goes to Paris with Sabrina, he'll be admitting he loves her. So Paris becomes the symbol of love; it's literally where you go to be in love. Otherwise you stay in dull New York adding up figures, and where's the fun in that?