Today I've came to the conclusion again: A VPS - virtual host - is not a good solution for my Drupal websites. It's great for development, but once you get traffic, the VPS operating system overhead kills pefromance. For real life, a non-loaded shared hosting plan is much better, especially one which is configured for Drupal. The site http://drupalmodules.com is using a shared hosting provider. Still - it preforms very fast.

If we need several domains, a good reseller package is more cost effective. Reseller packages are packages of shared hosting accounts - you may resell accounts with their own control panel and bill your clients.

The maximal perfomance and security may be achieved with a dedicated server - but for a hefty price. Dedicated servers also requires more maintenance.