I am planning to buy a prepaid data card for my tablet which I am using occasionally. I googled and found Singtel and M1 offering pay as you use data plans. Works well for my situation. When I look at the rates alone, it seems like M1 is cheaper. But Singtel offers 5MB of data free for every $10 top. So it becomes a little complicated. I started to wonder how much data I must consume before the 2 cards will make no difference to me in term of price. So i use Excel and set up a simple model and use Goal Seek to find the answer.
It took me less than 5 minutes find out using Goal Seek that the 2 providers will break even at $38.57 based on a data usage of slightly more than 19MB.
I compare again based on $10 top up and found that Singtel offers 30% more data than M1 even though the published rate is more expensive. Therefore, I am going to buy Singtel prepaid card later on.