I would guess that a large portion is spent on administrative cost. Staff salaries and salaries for the artist members and the conductor. Then there is the cost involved in getting guest artists. I don't know, but I would imagine that the costs in getting an artist of the stature of say Itzhak Perlman to perform with the orchestra would be considerable. I doubt that ticket sales, as exorbitant as some prices are, cover only a very small portion of the expenses of maintaining a viable orchestra, opera troupe, choir or other of the performance arts. Also in these economic times it would be unlikely that the general populace, at least in the US, would be able, even if they are willing, to pay the price for a ticket when survival is a greater priority (food, housing for the family, etc.).
All that being said, I can every once in awhile afford to attend a concert. As a matter of fact, I'll be going to a concert Monday (this evening, APR 18th). Going to be interesting to hear Canadian Violinist, James Ehnes playing the Max Bruch Violin Concerto No 1 in G minor with the Portland Symphony Orchestra. Actually, it's because of the Bruch and the orchestra playing Beethoven's Symphony #3 [Eroica] that I decided to attend.
Take Care
Tomas