Mechanic detected transmission code700 & 740 failed.Charging $1850.Is this O.k

Pick one , did you mean he is charging you $1850 to replace the transmission ? its not clear as for what else could happen its a honda the sky is the limit timing belt /water pump/head gasket/fuel pump/sensors = there a load of them /relays/vetec and or associated components/ cat converter/ABS system / axels/EGR valve , when you think of all of the systems on modern cars its cheaper to run a pre 1971 vehicle as they dont have all of the green emission crap and are lot eaiser and cheaper to repair !