IS THIS BAD OR NOT ( READ BELOW)

A happy Sunday to everyone, I hope you all had an awesome service,for those who attend church.
Normally in our church we usually do have Sunday school by 9am whereas the service starts by 9:30am.
A Sunday school is a kind of class that engages people to interact one on one with the teacher, a Sunday school is like an interactive class whereby the teacher teachers and the congregation asks questions after the class.
So today was one of those Sundays where there are rooms for questions, which brings me to my article of today, A woman asked a question today which got a lot of people giving their own answers she asked

"if you are a business person and someone refers a client to you and the job you are to do for that person is worth $200 but the person who referred the client asked for you to put or add his own percentage because he referred you to the client now making the quotation that will be sent to be around $300, is it a sin or a bad thing"

So when this question was thrown I was like it's a bad thing to do, but when I heard from others point of view , it got me thinking, with the present situation of the country, people tend to do jobs that are not even in their line of business, many people have become middlemen in other people line of job, take for example a friend of mine who rears catfish, snails, etc now takes job of constructing local ovens for cake and the rest, so you see when he gets job to creates oven and he give the job to the person who actually can construct it, he tends to tell the person to add his own cut of the money and bills the client.

So I want to know your own suggestions to this. Is it bad or not,? if not bad how do you justify it?