Apparently, since the gates were put into operation, ticket sales at Forest Hill have gone up 16%
While I hadn't heard the figures for Forest Hill, John Oliver (from Southern) claims that they are selling an extra 200 tickets a day on the Sydenham Town forum video. That represents an increase in sales of around 2% which seems far more realistic.
A 16% increase in total sales would require an extra 2010 tickets a day from Forest Hill. I'm sure we would all have notice the extra queues if that had been the case