haven't used igerslike's mention service, but hopefully someone can help you out!
^^ Please...just no.
OP, how have you tested it? How many mentions did you do on your picture(s)?
The method itself may not be as effective as commenting but that's why commenting costs a shitload more...can't blame Igerslike for that.
There are people doing 1 million mentions and gaining 10's of thousands of followers..
Do you use a custom list of usernames or scraped by #tag? I believe the scraped usernames may duplicated for different clients causing users being pissed tagged over again.
I use custom list so every user i mention is unique!