A broker is required to keep 50% of whatever position is taken in cash. If a broker is not taking cash from you, it means they are putting their own cash or funding it. There are two ways to recover this funding cost, either charge higher brokerage or recover the cost of funding.
In our pricing model, we recover the cost of funding by charging interest. Traditional brokers charge a % brokerage, so they can recover this cost from the value of your trade. There is no way around this. You either pay flat brokerage and funding cost, or you pay % or per lot brokerage and no funding cost.