Same question was asked on the coder section a few times over the past years. My take on it : that market is not so much about the tool, but more about the service offer, an up to date tool with maintained databases, an experienced crew with a long term commitment, forum, skype contact, and a stable user community that share databases and templates. Most gladly pay 60 bucks for scrapebox or a few hundred a year for seNuke. Seems they found their spot in the market place and everyone is satisfied with the situation. 99% chance a free open source project runs out of steam within 2 years as no one is going to do the skype helpdesk 24/7 and maintain databases for free.