Thanks, but not really practical for small businesses/small non profits such as I represent – it’s $300 a month on top of a Pro or Enterprise plan from what I can see. Other email service providers handle this with a simple CNAME record in DNS, the same as you do for DKIM, to set the Custom Return Path for SPF alignment with DMARC. ActiveCampaign/Postmark is one example and it doesn’t cost anything to do it either! 
Google and Yahoo may not be doing it yet, but its only a matter of time until they do given the junk mail epidemic isn’t going away. Since sending email is such a big element of the HubSpot service, it’s just surprising your only way to support it is a very expensive dedicated IP address.