There isn't any additional fee to use our API for the account. The only concern I might have about how many people you have accessing the one account is you may inadvertently run into one of our traffic limitations. Standard API Keys have a limit of 4 calls per second, and 10,000 calls per day. If you have too many people trying to access at the same time, you may get an error that you have hit this limit.
Please let me know if you have any other questions!
API Support Specialist
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