I believe this is known but it bears repeating, there's an unofficial website called iVisa that will appear first in your Google search, they'll be glad to take your ETA application and then charge you a $90 processing fee. I started down the road with them until I detected a foul odour.
Here's what Google AI has to say about them:
iVisa can be a convenient option for travelers seeking to simplify the visa application process, particularly for those who find government websites difficult to navigate. However, it's crucial to be aware that they are a third-party service charging premium fees, which are often considerably higher than direct applications through official channels. It's recommended to compare iVisa's fees with the official government charges before proceeding and consider if the added convenience is worth the extra cost. Additionally, carefully reviewing the application details is crucial, as some users have reported errors or miscommunications with the service.
Here is what the official UK site has to say:
An ETA costs £16.
Other websites may charge more to apply. Avoid websites that imitate government services.