What should an evaporators core replacement cost be?

Do not be so hasty to condemn the evaporator just because you can’t see the uv dye and smell something unusual inside the cabin.. There are simply too many other possibilities.. Additionally - the refrigerant (Freon) is odorless .. It is common to have a smell when the system is working due to the moisture collected in the HVAC or evaporator case. The system has likely been dormant for awhile - now that it has been operational - and condensation has the components wet - you get this odor - which is likely a stale smelling odor that is temporarily more pronounced now from the lack of system exercise. Of course this does not rule out the evaporator core as a suspect - however all other possibilities should be thoroughly investigated and it be proven where the leak actually is - evaporator replacement is going to be expensive! Good luck!