Can you replicate this with another device? It sounds as if the Uber app on your phone may not have accurate location data.
I don't have another device, but when I setup the pickup, I can pinpoint my location exactly in the app - it gave me the false price, then I switched to Google Maps, got the "correct price", then immediately switched to the Uber app from Google, and the prices that were listed from the original search quickly updated (like by 50%) without changing any location information.
Now after I spent the Amex cash balance down to zero - guess what happened - the behavior stopped.
This is looking more and more like a scam, and I think it would be helpful for other forum members to do their own tests and report back to make sure it can be replicated across accounts and devices - and if we get more reports of this behavior, then I think the media should be notified, unless we have an attorney in the group who wants to try and extort a settlement from Uber.
I don't think this is something Amex is doing - however who knows if they are aware of it or not. Like I wrote upthread, this type of behavior is right in line with how Uber does business.
To do the test, I would suggest the following approach:
1. make sure Uber and Google Maps are not running on your device - kill them from the sleeping apps list
2. make sure you have a positive cash balance in your Uber cash account from Amex
3. open Uber, setup a ride and get a price - then if you have Lyft, do the same thing and compare - if Uber is way above the Lyft estimate, then you have a valid test to move forward
4. leave Uber open, but switch to Google Maps, setup a from-to directions and choose the ride hailing option
5. check the price from both Uber and Lyft to make sure they are in reasonable alignment
6. click the Uber link which will then re-open the Uber app directly from Google Maps, and you should see the prices change to match what was in the range quoted by Google Maps