You are estimating 60624*30 = 259,200 calls per month.
As shown on flightaware.com/commercial/fligh … _class.rvt that level of usage will qualify you for the “250,000 - 999,999” usage tier, which means Class 1 queries will be only $0.0030 per call.
Therefore, the total cost will be 259,200 * $0.0030 = $777.60 per month.
However, it’s very likely that you can use the “Search” function (Class 2) instead of the SearchbirdeyesFlight (Class 1), which is a little less expensive ($0.0020 instead of $0.0030).
Also, you might consider changing your program to not make the same number of requests at all times of the day. It is very common to be able to reduce your frequency during night-time periods when there is less flight traffic occurring. You might also consider using pushed alerts, which will let us send you notification when something occurs instead of you making requests constantly.