What is the determining factor related to furnace cost? Is the same exact furnace that is say 75k BTU cost less installed than a 120K BTU unit?
for the exact same mdl furnace, the dealer cost difference between a 60KBTU and an 80KBTU furnace is inconsequential.
now, how the dealer prices it to his customer is an entirely different matter.
Bells and whistles, blower motor, efficiency, brand,type of high eff furnace-ie two stg, three stg, full modulating are the factors that determine cost. that's for equipment only-then the install has to take place.