I mean, the 100 USD bill is NOT the highest valued bill in the world, that belongs to the former B$10000 bill (withdrawn) from Brunei (I’m serious, this exists) which is worth $7874 and yes it’s a single bill, also converting to around £5803 & 6677€ respectively. Like why does this bill even exist when it’s hard to encounter, given that Brunei is a petro-state, it comes as no surprise.
The second highest valued bill is Fr. 1000 ($1278) or £942 & 1084€ which isn’t a surprise for Switzerland to have that due to how expensive it is over there. But, it’s difficult to obtain even in Switzerland and has advanced security features making hard to counterfeit due to its high value (x12 times of $100) but they sell stuff that’s over Fr. 1000 anyway so it makes sense for them to have that.
The reason why they are barely featured in crime movies or mentioned in real crimes relating to counterfeit money is because of their obscurity and the fact that they don’t know both exist (but it does, although either really hard to get your hands on it or ceases to circulate) however still retains their face value. The Swiss Franc is deemed a “safe haven” currency while the US Dollar isn’t.
It isn’t definitely the most counterfeited, it’s the most identified and most profitable. Hand over a $100 note and the pen comes out. Hand over a $10 and it doesn’t. If you’re bleaching a $1.00 note the $100 is the most profitable, but the $10 not is the least likely to be identified. $20 is a happy medium and if I had to guess the most likely to be professionally counterfeited.
It’s an interesting question because the statistics are only based on identified counterfeits.