That's only a good price if the membranes are OK - new membranes will set you back £120 and a carbon pre-filter
is £20.00
a new unit is £230 to £280 depending on where you get it from.
They can be a little more wasteful than slower RO's - but the speed/ rate of production is there key attribute - with water pressure at 70 psi you can make over 100 ltrs an hour
if you are not fussed on making it that quick then get a small one from ro man
filter available from Wrekin water supplies or WCW
Darran