You're mistaken about the deal. From the Sopranos wikia:
In Season Four, Artie approaches Ralph Cifaretto for a $50,000 loan.
This money would let him act as shylock to Jean-Philippe, the brother
of the new French hostess at Vesuvio, who needed $50,000 short-term to
fund a business venture. Ralph denies Artie's request on the grounds
that if Artie couldn't pay him back, he wouldn't be able to hurt Artie
in revenge because of his close relationship with Tony.
Tony finds out, and is hurt that Artie didn't come to him first for
the loan. Tony agrees to lend Artie the money on relatively generous
terms (1.5% interest) and Artie, in turn, lends the money to the
Frenchman on more strict terms (12.5% interest). Jean-Philippe
defaults (as he was scamming Artie the whole time), and Artie, seeking
to force payment, visits him to rough him up—only to get beaten up
Despondent and unable to repay Tony's loan, Artie attempts suicide by
overdosing on pills and alcohol, calling Tony before he loses
consciousness, sobbing, "I love you and I'm sorry I let you down."
Tony had been in a fragile emotional state to begin with because he
had just learned that his ex-comáre, Gloria Trillo, had committed
suicide—which he blamed himself for. Tony calls 911 but is angry when
he shows up at the hospital because of Artie's lack of consideration
for those around him in attempting suicide, asking him, "Suppose I
come over to your house and find you dead? How am I supposed to feel?"
Tony tells Artie that he'll assume the Frenchman's debt (including the
interest), and collect it himself, if Artie agrees to cancel Tony's
$6,000 tab at the restaurant. Artie agrees, but suggests that Tony
knew how the whole thing would play out from the beginning (Artie
would get suckered and fail; Tony would benefit twice by taking
collecting on Jean-Philippe's debt, and get his restaurant tab
erased). Tony becomes irately indignant over this suggestion and
storms out, telling Artie not to tell anyone about either their
arrangement or the suicide attempt.
The two don't speak to each other for the rest of Season Four, and
into Season Five; although, Tony still frequents Vesuvio during this