Yes, each coin you can buy or sell in the Voyager App is subject to a maximum order amount, defined in USD terms, that varies by coin and from time to time based on liquidity conditions.
Very liquid coins (meaning coins for which Voyager has access to many markets and there are many buyers and sellers available to whom we can route orders) have larger maximum order amounts, and less liquid coins have smaller amounts.
The amounts are currently not displayed in the app other than in response to an attempt to enter an order for greater than the maximum amount that is then applicable to that coin. For example, the maximum order amount for Bitcoin might be $250k, and if a user were to enter an order for $300k, they would be displayed an error message indicating the issue and alerting them to the then applicable maximum order amount.
Voyager is working on improved UX around communicating maximum order sizes by additional methods without cluttering the user interface.