ThunderVPN charges high fees due to several factors:

1. User Traffic: With a large user base, thunderVPN must handle significant server load, requiring more resources and thus higher costs.

2. Server Load: The extensive use of servers on the serverside necessitates additional servers, increasing server load and resource requirements.

3. Content Traffic: The wide range of public Wi-Fi sites generates extensive traffic, necessitating more bandwidth and resources to manage.

4. Customer Support: Maintaining customer support and resolving tickets increases operational costs.

5. Technical Requirements: Increased server numbers and higher bandwidth demand lead to more hardware and processing time, driving up prices.

6. Encryption Costs: Encrypting large volumes of data, especially with numerous encryption keys, increases storage and processing requirements.

7. Market Competition: To maintain market share, thunderVPN must set higher prices in a competitive environment.

In summary, thunderVPN's high fees stem from handling a large user base, server load, content traffic, support requirements, technical needs, encryption costs, and competitive pricing.