Prospect asked about e-mail campaigns, How much do I charge for this?

I have started to build my own local seo company. I got a referral from a past client who I built a site for. The prospect is asking me to setup an e-mail campaign for a list of people who subscribed to her mailing list that buy clothes from her online store. I know that I could probably use something like constant contact or mailchimp for this. I usually offer local seo help starting at $500 a month but never got into doing e-mail campaigns. For people with experience with this how much should I quote her to do this service for her, should I use constant contact or mail chimp? Thank you for the help.