According to Alpaca's website and as ONLY documentation I could find (or anyone else from their forums) they are commission free BUT charge the regulatory SEC/FINRA fees. From SEC and FINRA I have:

1. SEC $22.90 per $1 million sale
2. FINRA $0.000130 per share for each sale of a covered equity security, with a maximum charge of $6.49 per trade

So just as I started making real money with my algo... here comes something unexpected and very opaque: Many times the SEC fees for no reason at all.

Typical example: I made a volume of $ 2 million trading on a certain day... bam! $200 fee. And the worst is that they classify those $200 as REG fee on the statement I downloaded. FINRA is $1 which is in line.

Contacted support and they are pretty silent after redirecting me to their generic page which doesn't mention anything and after I confronted them with a math showing I should have been charge $40 bucks not $200.

Anyone else has this issue? Thankfully I have other options.

I also made a complaint to investor.gov so the SEC will contact them regarding this.