Steve, You've probably got the wrong time frame on when the $75 was listed. Yes, today, and even in the 1990s, major orchestra players made more than that. But there was an earlier time when that was good money indeed, especially for women.
You've never heard of Dennis Brain? Or Barry Tuckwell? Odd. Herman Baumann would be less of surprise. There aren't a huge number of notable horn soloists, but there are a few now and were a few back then.
There are many concertos written for piano and violin, fewer for cello. Fewer still for horn. But you'd be amazed at how many there are. Here's a list of horn concertos by well-known composers. It leaves out concertos by other, lesser-known composers; that list is even longer: Bach, 1, Quantz, 4, Telemann, 6, Vivaldi, 2, Danzi, 1, Michael Haydn, 2, Joseph Haydn, 4, L. Mozart, 1, W.A.Mozart, 4, Bellini, 1, Franz Strauss, 1, Gliere, 1, Hindemith, 1, Jacob, 1, R Strauss 2.
C