PHP/SQL vs. HTML - speed
 

Ok, I'm planning helping move a customer site which is a picture-based site, to vBulletin. Right now it's straight HTML, and CPU usage for apache rarely tops 1% (http tasks sometimes spike to 10% (only for about 1sec) but all http tasks on the server are usually below 1% CPU usage).

There's a rather large amount of pictures - which will become attachments - and I'm wondering if making them available as PHP->MySQL queries is significantly more CPU hungry than the current HTML requests.

There's just over 240,000 pictures to be moved, but we're using a batch system to do it and it's migrating very smoothly. Right now the site flies with absolutely zero lag, being HTML based. I'm just scared that making everything dbase-driven will bog everything down. How much more CPU time is required to handle the site through vB than it currently is through html ?