A B-list artist will get between $1,500 to $3,000 + expenses per appearance depending on the venue, the orchestra/conductor, who/where they are in their career, how big the budget is, and who is paying for the concert. I've had two students managed by Herbert Barrett who got that much about 12 years ago when they were still quite young. Rates have not gone up much because of the economy. Management commissions come straight off the top of that. And of course, sometimes volume discounts can apply.
If it's a standard work that's not too difficult for the orchestra, or they're very familiar with it, the artist will get two rehearsals plus some private work with the conductor, sometimes virtually. That means one rehearsal a day or two before, and the day of the concert. If the work has a difficult ensemble and the piece is unfamiliar, they might do a 3rd rehearsal. An orchestra with a smaller budget will only do two rehearsals no matter what.
There's a very famous, and possibly mythical, story about how Rudolph Serkin was asked to step in to play Beethoven 5 with the New York Phil the day of the concert. Serkin and the conductor knew each other and the piece very well and had done it the season before, so they made all the arrangements by phone. Serkin had another commitment right before, so he just showed up 30 minutes before the curtain to play the thing. Why rehearse when you already know it, and you've done it a million times? Serkin came on stage to thunderous applause, sat down at the piano and waited. The conductor started waving his arms around, and the orchestra started to play the opening chords of the Tchaikovsky.
So much for rehearsing, or practice. I'm told Serkin played very well nevertheless.