FYI 134A on sale for $2.99 12 OZ cans
 

If you have a Menards in your area, 12 OZ cans of 134A are on sale for $2.99 per can. No limit. 11% of the cost comes in a rebate. Very simple to get. If you don't want to mess with the rebate, still only $3.36. Charge an average system for around $10.00. Hard to beat.
On sale until Aug. 15