I'm very skeptical of systems that claim to help with trading signals. Primarily because if you had a system, then you would use it yourself. Trading is pretty much a zero sum game especially when it comes to signals. If you had a profitable signal and you publicized it, it would disappear almost immediately.

If your performance is correct and you're getting 200% per year, why sell the sauce for $20 a month?

I would just post the historical and open trades. Charge a subscription if you want to get exactly when you're selling them, otherwise release them on a few week lag to incentivize subscription. But give the rest away for free as you want others to pile in to your trade.