Bit of background first. I have an online money making project where I provide (well re-sell) facebook likes, twitter followers and youtube views to a certain niche market. I do most of my marketing to my niche audience through twitter where I have quite an engaged audience. I help them out, provide relevant content, promote their stuff etc so they don't mind me pushing a link on them every now and again. Someone has contacted me wanting to advertise on my twitter account. They provide a service which my niche audience would likely be interested in. For this service they would be charging anywhere between $250 to $700 (from what I've seen it's a top quality service and probably well worth it, they've worked with some celebs before) and want to trial advertising it on my twitter page for one week. They want to know how much it'll cost for me to post one of their ads / promote them every couple of hours for 7 days. I'm not sure what to charge. Any opinions?