re: Costs "relatively low?"
"Estimated cost just in the United States, just to convert refrigerants, ranges up to $130 billion, although exact costs are hard to figure."
I was thinking loosely thinking in terms of tens of billions and relative to required measures to cut CO2 emission for GW- tens of billions is cheap.
But the more of think of it, you are probably right and could easily in 100+ billion range. Perhaps, costing more money than war and reconstruction of Iraq.