Zona Colonial to Boca Chica with Uber is 800 pesos. Never had a problem with the driver asking for more. I think the airport problem is the taxi union bullying Uber to charge more.
I have run a tourist business in ZC for many many years and I can assure you that there are very few Uber drivers who will go to Boca Chica happily for 800 pesos. I have seen tens if not hundreds of tourists being refused by Uber drivers when they put in destinations out of town.