Today’s copper and steel prices are going higher and higher, and as a result, the cost of air conditioners, furnaces, and all other HVAC equipment is also rising.  There’s talk that these costs could continue to rise in the next few years.  If you have a 10+ year old A/C with R-22, it’s probably better to replace it now, rather than a few years from now.  Who knows what the price will be then?