Depends on steering, $1500 or less for EZ steer,, I think they are a bad joke. $3-4000 for EZPILOT,, they are ok, & depending on used/new $2500-6000 for a NAV2 & autosteer valves.

 Field IQ is what I think it takes for a FMX to control the booms on/off, see used 1s for $1000 or less, new I think is around $2000. It can use current electric boom Valves. 

I am still using a TRIMBLE 500 RTK to steer/control rates & a EZBOOM for the valves. I would like a FMX & Field IQ, But then I'd have learn a new system. 

These prices are just the stuff needed, no labor.

2 savings with AUTO shut offs, #1 not "dinging" crop by over/double  applying, #2 chemical.

Someone SMARTER hopefully will add to this.