You didn't get the facts right. You can use akismet for free, as long as your site doesn't produce more than 10.000 pageviews a month and you use no ad- or affiliate-program on your page.

Everbody else has to pay, so it's not a matter of "Do you make money with your blog". As soon as you site get's popular (You can get 10000 pageviews quit easily), you have to pay.

Beside the costs, Akismet has major privacy issues. Comments are sent together with the IP and mail adress to a outbound us-based service, which analyses and stores the transmited data. In Germany you could be sued because of these privacy violations.

With AntispamBee or NoSpamFX there are Wordpress plugins which stopp spam comments without the need to pay and without a privacy concers. My blog get's about 120.000 pageviews a month, i would have to pay $100 a MONTH! I would be happy if the site would make me a hundred bugs a month out of ads...

On my blog http://linuxundich.de there is no comment moderation, valid comments get posted to the blog as soon the writer hits send. To get rid of comment spam I use AntispamBee. During the last months I had to delete only one or two spam comments which where able to circumvent AntispamBee (Some people post spam to forums and blogs as their day job...). About 1000 spam comments get blocked each month.

I think that I've got even less work with AntispamBee, than with Akismet. Akismet marked Ham as Spam quite often, so that I was not able to purge spam comments automatically. Each day I had to check 50-100 possible spam comments for false positives. With AntispamBee i don't have to do this anymore.

To put it short: Akismet violates the privacy of your commenters, could cost you a lot of money and is not the best technical solution. Get rid of it and use AntispamBee or NoSpamNX!