If they did a flow and a pressure test, they would have determined if the pump is not pumping up to rated value.
Type: open center
Capacity: 15 gal [56.8 L]
Pressure: 3000 psi [206.8 bar]
Total flow: 23.6 gpm [89.3 lpm]
12.2 gpm [46.2 lpm] (loader)
16.3 gpm [61.7 lpm] (backhoe)
Price seems way out of line. What did the tractor cost new?
A 2003 list for $20,900
That is pretty steep! I'd wonder if the pump could be rebuilt. Seat of the pants - a new pump is probably in the neighborhood of $2K - but even at $100/hr shop time; you'd have to work quite a while to burn up $5K.