The bells and whistles are needed to even know if its functioning or not. How will you know your water pressure or TDS without them?

If price is the issue look at the BFS161 75 GPD for $169 here:
www.buckeyefieldsupply.com
It comes with a 1 micron prefilter, 0.5 micron carbon block, same membrane and probably same DI but gets you a inline pressure gauge, thermometer, handheld TDS-3 TDS meter with temperature readout too and a DI bypass so you can use RO only water too.

You won't get the treated and tested high rejection rate RO membrane or the custom blended DI resins, both of which save much more than the aditional cost but its a good value.

Its hard convincing someone to look past the initial cost and look at how much it costs to operate a unit over time, especially if they have never owned a RO/DI before but it is important.