I run three successful trading systems on collective2.com - one of the web's best platforms for trading system providers). The usual monthly subscription fee is $95 per month per system. Currently 50-60 subscribers follow the systems. Over 5 years over 700 investors / traders have subscribed to the systems.
collective2.com is an excellent platform but there is a much bigger international market that brokerage companies have access to. Brokers are specialist in marketing high performing systems to existing clients and prospects world-wide. Examples of these brokers include: www.striker.com and www.worldcupadvisor.com.
A high performing system can attract up to 500 subscribers at each company. Subscribers typically pay $100 per month per futures contract traded. i.e. if a subscriber is trading 5 contracts in their account they would pay $500 per month to trade the system. Monthly revenue can increase significantly as the system's performance history expands over time.