cTrader spreads start from as low as 0.2 on majors, and the commission is 3.50 per lot of the base currency 

of the pair traded. This is charged when you enter and when you exit the trade.

You can use the cTrader commission calculator to calculate the commission for different trades:

As standard, the commission is calculated as $35 per $1million USD traded.

FX example- If you are trading 1 lot (100k) of EUR/USD, the commission will be €3.50 when you enter and when 

you close the trade (€7 overall).

Metals example- (number of oz X MP) / 1,000,000 X 35 = One way commission