ask someone who heats their house with propane - then compare!
along a more Socratic tangent ...
propane: buy a tank, and go.
nat gas: hire a plumber.
propane: brew anywhere you want.
nat gas: point to where the plumber should run lines.
propane: get a burner
nat gas: get a burner
propane: first batch costs you 120 bucks.
nat gas: first batch costs you 350 bucks.
propane: get yer ass back in the car, AGAIN.
nat gas: go make beer. for almost nothing.
propane: my rig still looks all rusty and ghetto-ass.
nat gas: Oh, my! I have a varnished, modded, brewery in my basement.
propane: I have beer.
nat gas: I have beer.
propane: yeah? well I can fry a turkey!
nat gas: Um, well I get that GRILL over there to do that for me!
propane: I hate you.
nat gas: Have a good time in the shed this winter.
how much is your time and gasoline worth to you, getting a tank or two filled? monthly?
p.s. my grill is hooked into my house, too. i use it 100 evenings a year, and didnt see ANY blip in my bill ("um, DUH, because when you use the grill, your stove stays OFF!")