A person like that sending inquiries to website/API operators demanding data, ignore it. Always. Continue to ignore it until a process server actually shows up on your doorstep and serves you, in which case you know they're at least moderately serious, and then you need to engage your own counsel to deal with it.
If meeting the court's (or court parties') demands costs you something you are generally entitled to charge them for it, within reason and with justification.
As a hobbyist therefore putting a service offering page together with your preferred rate probably helps establish the nature and parameters of any such service.
Bill rates / piece rates, especially, and setting up bounds of what is reasonable to expect, in proportion to your gig and your intended effort level.
Quantity and price tiers, turnaround times, what will be included in the deliverable, how it will be delivered, SLAs, etc.
Whatever defines your service, esp as it relates to the types of requests you end up getting.
This is not a hobby, it’s a job.
This is why all my hobbies are dark web projects, these days.
Merely listing prices (without an associated automated payment form which could imply a contract was en force upon successful payment) doesn't actually force you to do business with anyone. It would however 1) deter requests for unpaid work by giving them an idea of what it would cost to get what they're looking for and 2) give you an idea of the demand for said services and could give you a warm lead which you can then choose to pursue formally by getting the necessary business structure, legal/business advice, etc.
In some cases it could. If you want to say "we categorically don't do X for ethical reasons", that can sometimes be more easily defensible in a way that "we have a standard price for doing this, but we don't want to do it for you in particular" may be harder to defend. (Even though I think both should always be possible.)