that's a good point that I've addressed in other posts, but perhaps not so much in this one. If you are going to use any of these services, it would truly be a waste of money to try using it on anything but your best quality posts. I'd even posit to say every post you make should be terrific and well thought out in it's own way.
This is your true calling card, and any attempts to attract more attention to yourself for mediocre content will likely attract little more than cold disdain and few (if any) new followers (and possibly even some a bunch of unfollows)!
It's also why I recently created and released a "Hide ReSteems" toggle button script for STEEMIT, so I can more quickly and easily focus in on a user's posts and see if the "quality" and "substance" of their posts are of interest to me. If I see 3, 4, 5 just great posts from a user, especially one right after another, doesn't matter if they've got 25 followers or 500+, that user will most likely get my follow, and my vote! :)
These services are also often used by other steemians to add additional rewards to a great post and/or just as a "thank you" for something else. For example, I've had a few fellow steemians such as @world5list tack on at least a few randowhale votes to my posts as a "thank you" for helping him "get up to speed" a bit faster with the STEEMIT ecosystem. Much appreciate @world5list, thank you again! :) He's also commented on the quality of my posts as well, so it's not as if such votes are appearing on sub-par content either.