For rent P3000 to P5000 a month will rent a small house in the province. In the city, figure P12000 to P24000 a month to rent a townhouse. Slum apartments can be found for as little as P1000 a month, but that is NOT recommended.
Food will vary, but if you shop carefully and avoid imports, you can eat well on P1500 a week. If you add in luxury items, it is easy to reach P3000+ a week.
Cost of medicines depends entirely on the health of the couple and how often they choose to visit their doctors. Health care is extremely low cost compared to private pay in North America or Europe. If you can enroll in a medical insurance that will pay health expenses in Philippines, then that is something to consider as it will stabilize expenses. Otherwise open a savings account with a Philippine bank and put a regular budget payment in that account to pay for medical expenses as they occur. This is one that will have to be watched to see what your actual expenses are and adjust the "insurance" payments accordingly.
Clothing varies greatly in price. If you are willing to dress like an ordinary Filipino, then clothing costs are fairly low. You can find fancy clothes with prices that would be considered high in Milano or Paris, you just need to check the big malls
Retirement visas with a pension requirement ask for US$1000 to US$1500 per month pension. So it seems that BI believes that amount is what a couple should have as a minimum income.
Plan on a few trips home to look around and see what prices look like in the area you are planning on settling in. Clothing prices, foods that you would be buying, check with the hospitals to get an idea of rates... All of these are extremely variable and will depend on your comfort level and needs.
The adventure continues