I imagine it might be free for citizens and similar groups, and at some cost for international visitors. You're best bet is to contact the health authority of the province you'd be looking to get it in
https://www2.gov.bc.ca/gov/content/health/managing-your-health/immunizations/covid-19-immunization
I'm not a resident of B.C.
Non-B.C. residents can contact their local Health Authority Public Health Unit.
edit:
Whether or not it's free for residents might also depend on the province, for example:
https://www.cbc.ca/news/canada/edmonton/free-covid-vaccines-bc-albertans-1.7615154
Albertans who don't qualify for free COVID-19 vaccinations in their home province can get one in British Columbia.
Which makes sense, it helps us here in BC if others are vaccinated since it limits the spread of the disease overall.