ChatGPT Plus is listed at $20 monthly, but the actual price you pay can vary...

https://gregorysbrilliantchat.lucialpiazzale.com/is-chatgpt-plus-cheaper-on-the-app-store-in-italy

ChatGPT Plus is listed at $20 monthly, but the actual price you pay can vary between $13 and $27. Differences come from taxes like VAT or GST and extra fees from app stores on iOS and Android