All MQL trading systems use a broker for trading.
A broker is a layer between a client with MT4 and real quotes in the foreign exchange market.
The broker's goal is to make money from their clients and the more clients the better.
For each lot, the client pays a commission to the broker, but this is only the visible part of the iceberg.
Brokers also like to use floating spreads in order to additionally profit from large spreads.
For example, for a leverage of 1: 500 for EURUSD, the commission for 1 lot is $ 4
If we recalculate the profit in points, for EURUSD it is 4 points of profit.
Usually the spread in the Real foreign exchange market for EURUSD is from 0 pips to 3 pips.
For example, if your broker uses a spread of 10 pips, this means that these 10 pips include a commission from the broker,
since in the market, as a rule, the spread is much lower.
Let's say a broker takes a commission of $ 4 and a spread of 10 pips for EURUSD.
This means that the commission is actually 10 pips + 4 pips minus the real spread in the market (about 0-3 pips)
In total, about $ 11-12 per lot.
Also, on the foreign exchange market, there are often not Real brokers, they are something like pyramids
The broker does not actually use your trades in the real foreign exchange market, because usually 99% of newcomers to the market lose all their savings.
I have been using Tickmill for my accounts for a long time and everything is OK