Why would you spend money so you can spend more money?

This question was posed to me by my 7 year old a while back and I’m still trying to figure out a suitable response.

Let me give you the back story.

Our bread and eggs delivery guy Sameer Bhai had just delivered 2 dozen eggs and some bread and I had to pay him Rs. 125. I couldn’t find change, so I asked him if he accepted Google Pay or Pay TM? He said No. But then told me that I could pay him next time but I insisted and he gave me a number of a friend whom I could transfer the amount to. I tried via GPAY but the transaction didn’t go through, unfortunately he didn’t have a smart phone, so he couldn’t display his QR code. After a while I gave up and gave him whatever cash I could find and he went on his way. The kids were in the hall and I mentioned out loud that I would love to buy Sameer Bhai a Smart phone so that he can start accepting digital payments, to which Izabela immediately remarked - Dad, why would you spend money so you can spend more money?

She then proceeded to draw this one the white board to illustrate her point.

She understood the situation, Sameer bhai’s feature phone cannot display QR codes, he needs a smart phone which costs approx Rs. 5000. Over and above that we have to pay him Rs. 125 for the bread and eggs. Hence, why would I spend money to spend more money. I was baffled. I wasn’t sure whether I was more impressed with the fact that I had managed to distract her from her screen long enough to engage with the problem or her training at school in being able to articulate the problem so lucidly on the white board!

I was about to launch into a long lecture on the circle of life, karma and how the more you give the more you get etc. but I just held my tongue and sheepishly asked for more time to think about her question and come back with an answer!

I still havent got back to her and I need your help with the answer. Why should I spend money so that I can spend more money? Let me know in the comments. Best answers get a dozen eggs and a laadi of best paav courtesy Sameer Bhai.