I only ordered four to start with for the studio. The bulbs are rated at 23 watts, each replacing a 85 watt flood. The new bulbs save 248 watts of energy and put off more light (equivalent to 400 total watts of light). The four pack of bulbs from the Amazon vendor ended up costing $5.87/ea including shipping. Buying more brings the cost down.
An unfortunate side effect of these is that the X10 dimmer doesn't seem to function with these in place. The X10 signal is being sent but must be getting absorbed into the ballast in the bulb because I couldn't make them dim. I'll be replacing the X10 dimmer with a standard dimmer. I'm worried they'll buzz when dimmed so I'll be holding the final verdict until I can test.