I ordered one off of Amazon.com around christmas time for 539.99 that was box and 1 collar. I dont know if its still the same price or not. You can try murrays hound supply or find Chris Murrays number, he was the second best price only like 5 or 10 dollars more than amazon.

Valley Creek hunting supplies they have a website astro 320 4 dc 40 collars long range ant sd card and pouch for 1200 even or try buzzard roost

Around Christmas Greentop in Ashland, VA had them around $740 for system, one collar, truck antenna and topo chip.

Look on Custom Collars website customcollars.com.
Terrance had the entire bundle with the long range antenna on there last week for $550. Not sure about extra collars, but I think they are about $199.

Gundogsupply.com has them for good price

I carry them the 320 bundle with topo card and 1 set of batteries sells for $579. DC-40 collars sell for $189. I carry other products for the Garmins Astro also. If you pay by check or money order I do better on the price. Give me a call Dog Box Man in Buena Vista VA 540-261-1344 ask for Mike.