Lessee, I'm paying $116 plus 6% sales tax for a wholesale purchase. I'm not sure what list is. They are not too tough to put in. You have to have room on the return or supply duct, maybe 18" x 18" roughly. You'll have to cut a hole in the sheetmetal on both. About 1' x 1' for the humidifier and a round 6" hole for the buc duct. I ust a stick-on 6" round tap in / take off for connecting the buc duct to the supply. You also have to mount a humidistat (supplied) in the return duct, small rectangular hole. Then you'll need a 24V source (they include a small 115 x 24 transformer) That all has to get wired together and somehow activated by a call for fan in the heat mode. Some units will have a termina designated for humidifier. There is a thermistor that needs to be mounted outside and that also has to get wired to the humidistat. Lastly you'll need a place for the runoff to go. (pump or drain) and you'll need some 1/4" copper tube to connect the water supply. They provide a saddle tap valve. I usually tap into the hot water FYI. Normally I'll get the whole thing done in 4 hours or less. Depends on how far I have to run all the wire. The drain requires a few feet of1/2" vinyl tube depending on how far you have to go with it.
It CAN be mounted on either supply or return. I usually put it on the return, but that's just me. No set rule, whichever works the best as far as room goes. The return is usually larger.
How far are you from Hartford CT? I might able to order one and have it drop shipped to you so you don't have to pay retail. Just wholesale and shipping.