Thanks for sharing...

For under RM200, this is my DIY 3-stage undermount POU. Cheapo standard 10" housing in series as mentioned by Billy boy with first stage RM4 1micron PP sediment filter, 2nd stage ceramic filter (forgot the price but not expensive) and 3rd stage is a good quality NSF certified Dalton carbon filter (I think around Rm40 to Rm50).
Maintenance is super cheap due to standard 10" filter.
I use this set up as my secondary POU point for washing and cooking food in the wet kitchen.
For direct from tap drinking water, I use 3M in the dry kitchen.