I agree that lack of clear pricing is a huge red flag.
Sometimes it's not even because of budget: if an employee can't experiment with the service using some free tier (not time limited, because other projects can urgently get in the way), they can't request whoever has the company credit card to subscribe even to the lowest paid tier, so they'll just try one of your competitors because blindly recommending a service that might be a bad fit is too high a risk for the employee's career.
Sometimes it's not even because of budget: if an employee can't experiment with the service using some free tier (not time limited, because other projects can urgently get in the way), they can't request whoever has the company credit card to subscribe even to the lowest paid tier, so they'll just try one of your competitors because blindly recommending a service that might be a bad fit is too high a risk for the employee's career.