In NYC the salary varies widely from place to place. Just to give you an idea. Some companies offer a base salary about 35K (USD) PLUS a commission based on sales above a certain selling point.
Be careful of companies who offer a commission based on "their" profit. Profit numbers can be manipulated in the companies favor and usually are. If you have the ability to know what company costs are you will have a better understanding of the real profit the company sees at the end of the job.
In NYC a kitchen or bath based on a contract that includes labor, commissions are usually 7-10% on the total contract.
Some companies offer a commission base as low as 5%.
IE: if you sell a million dollars in yearly sales with the proper mark up on materials and labor your net is only 50K before taxes. Yet the company usually has a real "profit" of 400-500K if they do there work correctly. Their "profit" vs your commission is disproportionate.
Other factors include your talent as a designer and your ability to sell, make the desired profit and follow up with the details making the job run smooth. If you have little or no problems with any of the projects your working on, your employer should acknowledge that and compensate you accordingly.
If your with a good company by all means stay with them. I'm sure they will work with you. Also take into consideration the economy. Hopefully Canada's economy is fairing better then ours.
Best of the day