Online trading costs

In general, a trader could incur the following costs and personal expenses:

1. Personal expenses: Your time, trading books, lessons, personal tutor, internet costs, computer depreciation, office costs, bots, etc...
2. Broker-based commissions, spreads and platform fees. 

Overnight and over weekend fees or refunds. 

Platform fees. Some brokers may charge a fee for using their platforms. Not very common these days though.

Slippage. Normally in volatile markets, the price may change from the moment you put in the order to open a position until the time it actually executed. Slippage can work in your favour or against you depending on the direction of price movement.

Commissions are payments to your broker generally as a percentage of your trade size and different trade sizes may incur different commissions, often referred to as tiers.

The spread is the difference between the broker’s buy and sell prices for any given commodity, stock or currency pair in pips. The buy and sell spreads are different; a complete list of spreads can usually be found on the broker’s website.

Missing on gaining interest by simply putting your money into a saving account.