R422d, R404a have very high GWP's so the price will rise and it is likely that these refrigerants will be withdrawn from sale early 2018. It is supply and demand. The chemical plants cannot just go and make some more. It is all on a quota if gwp. With regards to 407c as a replacement for 22, not a good idea. 22 worked with mineral oil. 407 works with synthetic polyolester oils. There will be a miscibility issue unless you have drilled the bottom of the compressor and done an oil change. Refrigerant issues are here to stay. R32 will be the last HFC for Aircon. See Kigali agreement for further info.