Agreed on the CTR, and ratio, if your site doesn't convert well enough from these perspectives it may not be viable no matter how big it gets.
Using Eros' example; In 3 months 45,000 visitors = 2 conversions. If we assume $30 PPS conversions... to get to $1,000 a month you'd need 750,000 visitors (22.5k visitors per sale). That would be a mammoth amount of work for very little return.
Get the CTR up, and ratio down by finding your best converting sponsors... then build traffic.
