I used these services in the start, but they are not profitable anymore, a few days ago, my friend bought a vote from #monnowbooster of worth 3 and in return, he got upvote worth 4.3 ? after deducting the curation and steem he got 4.6 sbd back and at that steem was trading at 1.8 i think, so he got 16 sbd and approx .9 steem. sorry to say it's not profitable anymore. I do remember when minnowbooster was profitable.