Depends if it's in or out of parts warranty, plus the type of motor. There is the standard PSC , X13 , and ECM all in use today. If in parts warranty , likely $175 to $ 250. If out of parts warranty $300 to $450 for a PSC, $595 to $795 for a X13, An ECM $1000 to $1400.
These are approximate prices, the vary greatly depending on your part of the country.There could also be issues, ruct ,etc. that would increase the cost.