cost 25 simoleons

Hello! 

Since yesterday (irl) my sims family are loosing money every now and again. -25 simoleons at a time.

It took me a long time to figure it out: It happens when they're on the computer. If a sim finish using the computer: -25 simoleons, every time. If a sim finish playing computer games -25 simoleons, if he starts watching funny clips on the computer instead -25 simoleons and another -25 simoleons when he leaves the computer. 

In my mind i thought it might have something to do with his work, because when this "-25"-thing started he just got promoted to investor. 

It's not a big deal for my family, they have plenty of simoleons and can steal more from friends and neighbours to compensate for the loss of using computors in the house. But I am still wondering what could possibly be the reason for this?

Have fun playing,

Jenny