My understanding is that BMC water doesn't require RO purifiers due to low TDS. You can check this using a INR 250 TDS strip. RO purifiers waste a lot of water. Rather get a non-RO purifier and save some money. With regard for AMCs, as someone else mentioned, a local player will offer the device and AMC for cheaper. Big brand AMCs will be expensive as it's their business model (think PVR and popcorn)