The comparison people actually mean, Martensville against Saskatoon, is not apples to apples, since Saskatoon's tax base is larger and its infrastructure is largely already built, while Martensville is still growing into the services a bigger city already has in place.
Assessed value matters just as much as the mill rate. A newer Martensville home built in the last decade generally has a higher assessed value than an older Saskatoon home of similar size, and residential property everywhere in Saskatchewan is taxed on 80 percent of that assessed figure.
Whether Martensville's bill is actually out of line for the property is a Martensville Board of Revision question, not a comparison to a different municipality's rate. Get your hand-reviewed valuation from Joel Dyck.