If you include time as a cost, then I think you've hit the nail on the head. In the beginning, it's good to make the process as simple and speedy as possible.
As for me, I got a Mr Beer for Christmas one year, and it worked so well for me, I've never looked much past it other than adding steeping grains to influence the beer's characteristics.
But now that I've tried it so many times, and I'm more willing and "adventurous" in experimenting with steeping grains, all-grain all of a sudden doesn't seem as intimidating/mysterious as it used to. And with the advent of BIAB, I'm seriously considering a batch of all-grain APA as a test. The bag isn't all that expensive for a try-out, and if I like the results... who knows? I might just stick with the AG BIAB. All I need to try it is the bag and an overhead hoist to get it out of the kettle.
Thanks to extract brewing, I already have everything else I need.