This issue could be split up into a few different issues really. But I'll leave it for now as a big one.

What's the rationale for charging for data? Seems it is not really using significant resources so has no real cost to the webmaster, and is very tangential to Composr as a product (i.e. it's a very specific business model that I don't think many would have any interest in).

I agree, I see no point in charging for data download. It's just something I read in the GDPR that you could legally do so after making the first download free.

For requests where a user is requesting specific data, rather than all data, perhaps a small fee might be applicable. There is also the question of which format a user's data is shared when requested. Email, Secure PDF etc. I think Freedom of Information requests work on the basis of being free except for more specific requests which may need special handling. Not sure whether a charge should be considered for dealing with specific GDPR requests, just comparing with similar acts which are free in principle but may have costs involved in practice unless everything is automated.

https://www.techrepublic.com/article/how-to-request-your-personal-data-under-gdpr/

"There is also the question of which format a user's data is shared when requested. Email, Secure PDF etc" - there's no requirement for any specific format, so it is just a dump in whatever format works for us. In our cases we are providing a partial SQL dump. Having data in a rawer format allows people to potentially do their own thing with it, while formatting it into a document would not.