RO is not expensive if u look at it in the long run. I had installed RO at my house and also recommended for my office which they have installed at all my office locations. Currently it costs Qr 2k including installation with filters. replacement filters cost Qr100 which have to be replaced every 8 months as the water we get is not that great quality (you should see the filter after 8 months) The quality of the water from the RO is like sparkling water its great. I have a family of 3, and its a perfect solution if your are staying in an appartment.
I know couple of ppl in office did a one week project browzing through the web and in the end decided its not good for young children!!! but now they are drinking RO water in the office!!
my personal advise go for it, I used Britanica water.... if you need their number let me know.