Google search results may show results such as "www.nexus-card.com" at the top of the search listings.
These companies are NOT the CBSA - they are private. They charge $100-$125 on top of the actual government fee of $50 $USD.
You do not need to use such a company to acquire or renew a NEXUS card. So, that's basically $100 for nothing.
When renewing, be sure you're dealing directly with the government. Correct renewal link here.