An HTML email service is convenient, but can get costly. So you need to choose a service that will be the most cost effective for your subscription goals.

I took five popular services and compiled the monthly subscription fees over the number of subscribers starting at 500 and ending at 25,000. These numbers assume unlimited messages are part of the plan and were compiled on February 24, 2013.

Monthly Price Comparison of HTML email services. Click to view the interactive version on Google Docs.

I stopped at 25,000 because some of the companies requested you call for a price quote for numbers greater than 25,000. 

At 500 and less, Feedblitz, Mailchimp and Vertical Response are the cheapest at $10 or less. At 1000, Vertical Response are half the price of the rest at $15. Feedblitz is at $29.95 From 1500 to 2000, all the services are about $30. At 3000, all are around $50 except for Feedblitz which is still at $30. At 4500, Vertical Response jumps to $72. At 5500, the rest jump up to the $70 and $75 level. At 8500, Vertical Response jumps to $120 while the rest remain steady. At 10500, Aweber, Constant Contact and Mailchimp rocket to about $150 and Feedblitz goes to $102.

Other Notes:

Mailchimp has a “Forever Free” plan if your list stays below 2000 subscribers and you are limited to  12,000 emails per month.

Please note some of these services do offer ala carte packages if you are not planning on sending an email at least once a month.