I agree the Trimetric is costly and you can get the basic info including an AH accumulation in /out count from much less costly monitors.
However I do prefer to have everything across the monitor's shunt for the full picture. Then it is easy to subtract what is solar by knowing what is the usual amount for solar out of the total the monitor is showing.
If all you have is the solar monitor, you have no idea of the AH count for the whole rig except by the "morning voltage" same as with no monitor at all.
Ideally, you could have the total on its monitor and the solar upstream with its own monitor for a more accurate idea of how much of the total is solar
This little solar $40 controller has an AH counter so why does Trimetric want $175 to do that? Answer is all the fancy data collection stuff Trimetric does for you, except for me, I don't use any of that, so the Trimetric is a very expensive way to do it.
http://www.chinasolarregulator.com/user-manual/solar30.pdf