i've seen computer stores which sells surplus or used monitors in makati (buendia-crispa, near Tropical Hut burgers) and in festival mall alabang.
i've also tried asking before to trade in our office CRT monitors to LCDs. mababa lang ang bili nila. a one year old 15 inch CRT monitor is only bought for 800 pesos. tapos dagdag ka pa ng 2k each for a used 15 inch LCD monitor.
what i suggest is ibenta mo sa tipidpc yung CRT mo, tapos yung proceeds, bili ka na lang ng used LCD monitor para di lugi masyado.
afaik, used LCD 15 inch monitors are still sold at 2.8k and above.