Hi Nikita,
I am going with Tom on this one. Google has made a obvious effort to cut down on web spam in all forms over the last year or two. This effort has included the devaluing of various types of links and various ranking penalties for sites it thinks are 'breaking the rules'.
Now you say these links seem legit, but the process of obtaining them is anything but. A fiver to get 15 links on edu sites that are in every way only there for the link? This is spam.
Regardless of if these links are going to have any benefit (agree with Tom here, I seriously doubt it but in some verticals you never know) the bigger picture is you are leaving the door open to future penalties and/or drops in rankings due to a dodgy link profile. I would never want to have to get into that conversation with a client!