Movement Industries Corp (MVNT)

[chemist72]

You can see how the size of the valve affects its price.

150 PSI Full Port 316 Instrumentation stainless steel flange ball valve 
 DESCRIPTION	                                                PRICE 
 3/4 inch 150 PSI Full Port Stainless Steel Flanged Ball Valve  $ 112.35 
 1-inch 150 PSI Full Port Stainless Steel Flanged Ball Valve	$ 145.43 
 1-½ inch 150 PSI Full Port Stainless Steel Flanged Ball Valve	$ 222.08 
 2-inch 150 PSI Full Port Stainless Steel Flanged Ball Valve	$ 311.85 
 2-½ inch 150 PSI Full Port Stainless Steel Flanged Ball Valve	$ 367.50 
 3-inch 150 PSI Full Port Stainless Steel Flanged Ball Valve	$ 656.25 
 4-inch 150 PSI Full Port Stainless Steel Flanged Ball Valve	$ 937.65 
 6-inch 150 PSI Full Port Stainless Steel Flanged Ball Valve	$ 2,341.50

A 6" ball valve is about 20 times more expensive than a 3/4" valve. The type of steel used and the pressure rating would also have significant effects on the price.

I also believe a digitally controlled ball valve would cost significantly more than a manually operated valve.