1. I doubt money enters the equation here, let's be real, how many 90s songs are being used now? Mostly on backwater radio stations let's be real (Especially the ones I mentioned), I'd say Barbie Girl might be more expensive due to the movie which was released but not by the amount which would make this game infeasible.
2. So, funnily enough I was talking to my mother about this, bringing up about the 90s thing and I remember saying "I haven't seen the list of songs, but I guarentee there's no Backstreet boys, Spice Girls or Oasis which were definitely some of the most iconic 90s hits" and we spent like 20 minutes sharing what we miss from the 90s, to be clear I was born in the early 90s so I was a kid and I have a more rock-solid memory of what it was like (Albeit, in britbong land).
Hell we were swapping "What things we miss" and I said "Oh definitely how everything in my bedroom was inflatable" and that's not an exaggeration, the 90s had a fascination (at least here) with 'blow up furniture', I had an inflatable sofa, an inflatable bin, my sister owned an inflatable coat and inflatable bag.. Shit was fucking wild.