Because corruption. As you point out there just is no other reason why we're paying more for our base model Chevy Spark than we'd pay for a Porsche.
It nod only robs Canadians but it robs us of a properly kitted out military. How can we afford new equipment when everything we pay for is two, three, four times what even our allies are paying, never mind what Russia or China is paying. How many frigates do you think China could build for $5 billion?
Wait! Google! Yeah! That's a thing. So China is building new destroyers - which are much bigger and more capable than frigates. The Type 055 is between 12,000-13,000 tons. Canada's new frigates will be about 6900 (9400 fully loaded). China's destroyers are costing it about $400 million.
So for those who compare militaries based on spending this is one of the reasons why that doesn't work. China can build ten of these big destroyers for the same cost as we'll fork out for one frigate.
https://www.businessinsider.com/china-largest-destroyer-most-powerful-055-lhasa-renhai-nanchang-zumwalt-2022-6#chinese-media-has-touted-the-ship-as-the-second-most-powerful-destroyer-in-the-world-after-the-uss-zumwalt-2