A flanged six inch is between $1200 and $1600.  Who you buy it from makes a big difference.  I do not think that you can buy direct.  If you do not have a dealer in your area, that may not apply.   We also buy water from an irrigation district and they recently replaced all the meters that are "active" with the same meters.  They now allow a 2 inch outlet to fill spray tanks.  The old (really old) propeller meters they had did not work with very low flows.