Ryouko isn't just a great scientist, she's also one hell of a businesswoman if she can plan for a switch in the target-demographic of their entire line of merchandise that quickly.
Expect a lot of sales drop for transformation items there. Henshin devices are always hot items for young boys but magical girls' items have a lot of competition on the market for young girls.
The time to show up the merchandise matters a lot too. A lot of shows tend to put out new toys near Christmas for guaranteed sales for example.
Predictable. I'm sure that boy is a huge fan of Thermal Blood and instead of Magical Girl figurines or henshin items, it's Thermal Blood merchandises. I can see that the boy hate the Magical Girl because he think that the Magical Girl take his hero's place.
I thought this manga would be all gags and shit but it definitely deals with some stuff realistically like the commercialization stuff and children's reactions to having their hero changed into a magical girl.