Are you trying to say this is something new? I grew up in the 50s and 60s and my parents bought me plenty of cheap plastic toys. Since none of them are still around I assume they went in the dumpster.
I question I would pose about all this offering of princesses and their merchandise is this. Do people want this stuff because Disney offers it or does Disney offer it because people want it? Maybe a slight bit of former but I say primarily the latter. The tail doesn't wag the dog. Disney offers all this stuff because a whole lot of people want it, like it and will spend their money on it.