Had this very conversation yesterday at the track at smoko whilst working the horses and of the 5 of us there, we all cut our breeding down. Between us there, we left 11 mares empty this season. Why? The consensus seemed to be pure and simple finances. I have a horses 3-4 wins that are racing for $1500 - $2000 less than than when they were maidens.
Having said that, I have had 2 studs giving a good size discount for two of my mares.