https://wowa.ca/calculators/commissi...ulator-alberta
If you use this calculator, you can see the estimated commissions on the sale. An $800K sale comes out to a little over $29K per this calculator. That's basically half the cost of the garage or essentially the cost of the top suite on top of the garage.
That's not factoring the legal fees, mortgage application, viewings, fuel, dual mortgages for a short duration(?), searching, annoyance and time and effort and costs of packing/moving. That's probably the equivalent of another few grand there as well.