Do CSP partners charge extra on top of Microsoft's list price?

It depends on the partner and the specific product. Some partners price at or near Microsoft's list price and make their margin through value-added services; others build a margin directly into the unit price in exchange for bundled support and management. Neither approach is inherently better — what matters is understanding the total value you're getting for the price.

The most reliable way to evaluate this is to ask directly for a transparent breakdown of pricing and what's included, and compare it against what you'd pay (and what support you'd get) buying and managing things yourself.