>Supposedly, they've been written by professional algorithmic traders

And discarded by them as not profitable enough for their own use.

This goes exactly against the point I'm making.

Those strategies are not a bottom up system that combines a tailored infrastructure with sophisticated trading models. BOTH are needed, TradeStation is absolutely NOT a sophisticated infrastructure. And I doubt that the models are sophisticated enough to rake in alpha, especially in terms of execution.

Maybe if you put in a little money you'll break even with the subscription cost. If you put in a lot, those systems will break down.

No one sells a profitable algo in an app store, those are worthless other than as samples of how to buy and sell and read indicators.