You're a trustworthy babysitter & those are hard to come by, well-behaved kids or not. $50 is not a lot for someone who will actually interact with the kids and who knows what to do in case of emergency...
Heck... when I was 16, I worked for a baby-sitting agency for the summer...they required you to be certified in CPR and basic 1st aid. The agency would call us & ask if we would like to sit at such-and-such a date from whatever time... mostly for the tourists who brought their kids with them on vacation. If I had plans (or if the sit was a child under 2!) I would say "no thanks" and they'd call the next sitter on the list.
This was 10 (or so
) years ago, and I was paid $9/hr for the 1st kid, and extra $2/hr per kid thereafter...there was a flat $4 traveling fee...and if the parents stayed out past midnight, it was time and a half. Double time holidays!
I was not allowed to take them to the beach (hotel pool only) or off property and I didn't have to cook (the parents either left food, money for food, or told me to call room service) .... I got to stay in some snazzy hotel rooms & sometimes even got tipped at the end of the night.
The best were the kids I could put down at 8pm for bed & spend the next 3-4hrs watching TV & occasionally peeking in to make sure they were still sleeping.
Good times.