We’ve rolled out some new pricing for commercial use based on the feedback you guys have been giving us. Pro‑blogger has remained exactly the same.
The first thing you’ll notice is the Enterprise access now has several price levels starting from $50/mo based on how many blogs you have. This should allow more flexibility for businesses just getting started out.
Second we’ve seen a lot of use of the Akismet API for things which aren’t blogs at all, like feedback forms, guestbooks, and more. For this type of use people might find it easiest to purchase commercial use based on the number of calls they make to Akismet, so we conjured up a new system called the Access API, which also starts at $50 a month.
Keep sharing your thoughts, and we’ll continue to make the service fit your needs better.
Akismet 
For a small commercial site (e.g. 100 fill-ins of a comment form) the new pricing is way too much.
A better approach would be to have AccessAPI not as a monthly allowance, but as a purchase of a number of credits. That way I can happily pass over $50 and keep a small commercial site spam-free for a long while 🙂