As Harold Duckett mentioned in the post below:

It usually comes as a surprise to audiences and to the public that the cost of rehearsal is the same as the cost for a performance, with added costs at performance time for the hall rental and associated staff.

https://www.knoxtntoday.com/takes-work-provide-play-kso/

Other added costs that often surprise audiences: instruments that cost thousands to many-thousands, maintenance and repair (did you know cello strings were hundreds of dollars, not to mention the annual reed costs of woodwind players), and instrument insurance. Musicians also subsidize the orchestra with their (expensive) professional training at many of the finest schools in the US and abroad. Lastly, there are sometimes medical costs to playing a musical instrument full time… ask a string player if they’ve ever experienced tendinitis or a brass player if they’ve ever on bruised lips (or worse.) The musicians on the stage of the KSO are professionals, just like professionals in any other field. We hope to see you at a concert soon, to share in the work that we do to bring this music alive for you.