The cheapest masters will probably promise you (not in writing) that it will for sure get you into dental school, no problem. Which wouldn't be worth it.
The only cheap GPA enhancement programs in the US are:
1. at public schools, but the cheapness only counts for US citizens who are residents of that state
2. at Tulane ACP, but you have to be on a med school waitlist to get in
And again, we really don't have much info about Canadian low GPA comebacks here.
Best of luck to you.