Typically, discount brokerages in Canada offer lower trading commissions for investors who have more than $50,000 in their trading accounts. However, there is usually some fine print that can lead to novice investors paying higher commissions than they expect.
A good example is Qtrade’s Commission and Fee Schedule page. It says that online investors with accounts that total at least $50,000 qualify for $9.95 commissions on trades. But a footnote says “You must advise us of these multiple account relationships.”
Just because you know that you have multiple accounts with your RRSP, RESP, and TFSA doesn’t mean that Qtrade knows. In practice, you have to tell them that all your accounts plus your spouse’s accounts should be grouped together. Otherwise, you could be paying $19 per trade instead of $9.95.
I went through this misunderstanding years ago with BMO and recently a colleague overpaid on a few commissions with Qtrade. It pays to read the fine print related to any fees you pay in your trading account.