I'd guess about $3K-$4K, probably closer to $4K.
Imo, you don't want a loud compressor running all day long. I see that those spindles are 60% duty cycle. Unless you need to run it all day long every day, I'd go with the fan cooled. We haven't had any trouble with our fan cooled HSD spindles at work. We just had an ATC spindle rebuilt due to some sensors going bad, but it ran a couple hours a day for 10 years with no trouble.