Since I don't have an exact site count, I've just bid the per-site rate for around 30 WP sites (I typically do one site for $50). Other platforms(Magento, Prestashop) have different rates.
Relevant Skills and Experience
I run a web hosting service and have extensive malware cleanup experience.
Proposed Milestones
$40 USD - WP cleanup, per site.
I'll need fresh, updated copies of any commercial plugin used in the sites. More info on chat.