How much does it cost to get an online gambling license? I know that it will be differ from one country to another but let us discuss for U.S.A as a reference.
Like you correctly said that the price of license differs from one country to another. However, USA is not a very friendly country to start an online gambling website. Majority of the US state law bans any form of gambling. So prefer countries from EU than USA. However, to answer your questions, I have found few resources which may help you to understand the situation in a better way,
Resource 1:
https://www.quora.com/How-does-one-obtain-an-online-gambling-license-in-the-United-States Resource 2:
https://www.gamblingsites.com/online-gambling-jurisdictions/Resource 3: (This company provides licensing support)
https://fastoffshore.com/what-we-do/online-gambling-services/Hope this helps!