If I were booking a hotel for friends or family and they were on a budget, I'd probably pick one of these:
- Best Western Plus (Hotel Europa) on Drummond Street
- Le Nouvel Hotel & Spa on Rene Levesque Blvd.
- Best Western Ville Marie on Peel Street
All of these are going to cost you about CAD$100 to $120 per night. There are cheaper places, like the Comfort Suites Downtown. And there are plenty of others downtown in the $160-170 range. But you wanted reasonable price and for what you get, these are pretty good.
Keep in mind that if you are driving to Montreal and need to park your car, there may be additional costs if you plan to use the hotel parking or a valet service. And parking is not cheap in the downtown area. If you do have a vehicle, you might choose to find a hotel that is outside the downtown core, to try and get a free parking location. Example might be Quality Inn near the airport, or the Sandman Hotel in Longeuil.