I can't really speak specifically to blog post rates so take my (limited) experience and advice with a grain of salt. But I just went through this recently so I'll share my tips and experience.
I was going to send you to those articles you mention because I think those are a good guide. In general, don't price yourself below the market, or at least too far below. You can tweak the freelance writing advice forumlas (
I like this one even though it's for web design because the formula is detailed, explained, and easy to tweak) to however much of a "full work week" you think the task is going to take. So if researching and writing the blog is going to take maybe 10 hours, and a full work week (used for the forumla in that link) is 40 hours,
you can slash the final rate you get using the formula by 3/4.
Don't charge full-time rates for part-time work, but don't undercut yourself either.
ETA: the above was expressed in a rather convoluted way and I think it's just going to lead nowhere good. Basically, figure out your minimum need. So if a project takes 10 hours out of 40 needed, you need 30 more hours of work or a higher rate to break even.
Always remember that a.) you are a skilled, professional practitioner of an in-demand craft (and yes, yes, writing is looked down on by all kinds of companies but yes, they have to pay for it if they want good writing, and they do, ultimately), b.) as a professional (you have other work and other tasks even if they're your own) your time is valuable and
you need to be compensated, and c.) when a writer charges way, way less than market the client assumes they're going to get shit work and/or doesn't care (which is worse), and that writer is basically telling clients it's OK to do this to other professional writers. Don't torpedo your industry--it's bad networking voodoo.
Example I can use because--Hallelujah!--the project I ran this for just fell through, as indie gamewriting gigs are wont to do: I took a rough estimate for what an entry-level game writer makes in a studio and used that as a target salary (not actually, but more on that below). Then I worked out an hourly rate based on a full work week minus vacation and adding overhead+expenses+etc.--see the link. Now I know pro rates, and I checked these against some specific rates posted by writers in other places for the same sort of work (so in my case, narrative design and scriptwriting for interactive, which requires 10x more time than scriptwriting for film because of the non-linearity; in your case, blog articles as similar as you can get to what you're writing). Then I did some math-fu based on the interview I did with the client, figuring out how long the task was likely to take each week. This requires some self-knowledge of one's own process. For the straight writing, I just looked at the timelines for the various one-act plays I'd written, which are a similar length. I wiggled a bit for expected revision and so on. This client also wanted consultation time, which is hairy, so I worked out a base # of hours for that and ended up at about 2/3s of a work week, which was WAY more than I had expected it would be before I ran the numbers.
Run the numbers.
Now, this client was a start-up run by a friend of mine. I loved their project. I know what start-up game funding is like and knew they couldn't pay me pro rates. So I did some more research, ran some more numbers, and worked out how much of that hourly rate I could hive off into a flat episode fee that would save the client some money if it took them a long time to implement the actual script (in games, it ALWAYS takes a long time to implement the script and nobody ever budgets for it). I also looked at my estimated hour counts and figured out how much I would have to cut to make the hourly consulting rate appealing to that kind of client.
The important takeaway of doing that was that I knew, going into negotiation, how my rates reflected the hours and needs of the project. That way, I can say, "Well, I can go lower, but I'll only be able to make X hours of meetings a week." This is both respectful to a client trying to budget how much they're going to have to pay and also respectful to yourself by making sure you get paid for the amount of work you actually do. Of course then their funding hit a wall and the whole thing is currently adrift for the time being. These things happen.
Prior to that point, I didn't have any idea of what I'd charge, ever, for a freelance project. This made for an awkward moment during the interview where I gave a swift mea culpa and promised to work something out quickly and get back to them. Doing this process--even all the adjustments--took me about 4-5 hours and was TOTALLY worth it just for the knowledge I gained doing it.
Remember that this may be wildly, wildly different in your industry and market and everything I've written may not apply at all. If others experienced with writing for content sites contradict me, go with them. I just think this is a useful process to have in one's arsenal.
Good luck!
