The nice thing about the geoDVR is it does the video multiplexing at the geoDVR firmware/software level so you can use almost any monitors and the operator can arrange their video feeds and map panels however they like.
We have seen clients have good luck with industrial options in the $500 – $2500 range. Given the value, many clients will go that way, unless it is a law enforcement or military aircraft.
Some of the advantages to going MIL-STD spec is extra durability and serviceability and extra features like night vision and programmable buttons and Dzus mounting. Most commercial/consumer monitors when they break, they are done, but again the value can often justify that.
We offer some 13.3 inch industrial monitors for around $500 USD and are also offering the mil-spec Viewpoint Systems displays (and others based on client request) and we are happy to help you select anything in between.