Their email campaign looks really good. The design has everything you want – fresh colors and clear design, a clear objective and minimalistic copy. They are doing a great job of keeping their emails very pointed with a clear CTA. In every letter, you will get guides to different cities. Like recently it was about Barcelona with its secret beaches and local places.
(j) You will not exceed, or if you build and release an application that calls PA API, each copy of that application that is installed by an end user will not exceed, any limit on calls per second set forth in any Specifications (or that we otherwise notify you apply) and you will not send files to or from PA API that are greater than 40KB without our prior written approval.
Website conversion is also a big issue. Affiliates often determine how much effort they will devote to promoting your product based on the Earnings per Click (EPC) that the merchant generates for them. This calculation is based on their commission rate and the conversion rate of your website. If you have a website that converts really well (gets people to make the purchase), you may be able to offer lower commission.
Whenever possible, add a personal element to your emails. Most email tools allow you to enter shortcodes that will be replaced with the recipient’s name when the email is sent out. Emails from Treehouse Co-Founder Ryan are always fun and personal. The subject lines are creative, messages are sent "from" Ryan's email address, and the content is personalized. If you reply to the mail, you'll even get a prompt response from Ryan himself!
But to go back and answer your question as far as typical ROI, I would just say roughly if a business implements a referral program, you've got to keep in mind that typically you're not paying these affiliates any upfront fee. You just paying a percentage commission for a referred transaction, whether it's a dollar amount, whether it's a percentage of their order total.