I have a paid app and can see the quota is 90,040 per day for channels created.
I have looked at all the pricing pages from cloud services and developer pricing pages and can not see any prices regarding the cost per channel created after the 100 free limit.
https://cloud.google.com/appengine/docs/quotas#Channel this page only says the daily limit is "Based on your budget" but I do not see any costs anywhere on the web.
Am I to assume that I get 90,040 free per day for having a paid app
As I understand the pricing changed recently and that's why the documentation is a little confusing. It used to be that you paid a tiny amount for each channel (something like 0.0001 - don't remember how many zeroes).
Now this tiny charge is canceled. You are just paying for CPU & bandwidth that your channels are using. That's why it says according to budget.
It's the same story with Email, and various other APIs as mentioned here: https://cloud.google.com/appengine/pricing. I'm fairly sure Channel API should be included in the last row in the resource billing table.