I bought one of mine used off of ebay and converted one to make a large incubator.
The other new from ebay lol
Anyway 6 females is 12 eggs every 14-21 days with 43-62 days on average to hatch, too mard to compute of how many you COULD have at one time with eggs being in and new ones coming all at the same time. But a standard hovabtor will not handle that IMHO.
Here is a link of how I increased the size of mine to hold more and the upgrade was really free since I got a fish cooler free from the pet shop to increase the size. http://www.dragonflyreptiles.com/incubator.htm