What is the line/acceptable limit of how much I can use a company's paid API to create my own product?

Here is a hypothetical example to illustrate what I mean (not actually my business):Google offers Natural Language recognition API.Let's say I offer news sentiment assessment service: The customer enters a topic, I aggregate various news articles, run them through Google's Natural Language API, then tell the customer whether the news around this topic is positive or negative.Google would charge $1 for 1000 queries, but I would charge x10 for that after my "news aggregation" twist.There is probably a clause in Google's API terms and conditions that I cannot create a competing product or resell their API or something along those lines. However, I am not competing with them directly nor reselling their API direct. Users won't be able to tell that I used Google's API in my algorithm.Is this allowed? I am asking in terms of Legality and Ethics.The above is not my actual business model, and I know Google is probably too big to care. But if Google was a smaller company, do you think I could get away with building my business based on somebody else's API?Similar to how Uber is using Google's maps. Without it they would have never gotten to where they are. Is Uber paying Google a fixed API fee (or I think it is even free) to use the maps? or is Google charging them a % of their revenues? see hubwealthy.com/wealthy