Could do (and have in the past). But it is a workaround, and takes extra effort.
A couple of our suppliers do have the separate-email-for-invoices-only thing, and it really is super convenient to know that any changes they make to their invoice emails (subject lines etc) won't break our forwarding rules.
Also the forwarding rules don't survive email migrations (which I admit is a super infrequent thing to do). When we migrated from Google Apps to Office 365 we lost the rules we'd previously set up for this type of thing.
Have you considered virtualization? Before adopting OSX, I went the virtualization route myself 4 years ago. I know it works on vmware (at least for me back then with vmw player running on Dell Linux laptop).
It probably depends on your requirements. YMMV
If you're going through this to save a few hundreds, get a mba refurbished.
I have Lion, Mountain Lion, Mavericks, and Yosemite running in VMWare Workstation. They work well enough to do web testing in Safari, but the video performance has been too slow to do much else, so I don't use them for anything too serious.
But then you dont get data about how much someone is willing to pay. Why not at least have your pricing table and underneath each pricing package, a signup for free call to action button with their own href anchor ( /signup#gold ) to track within google anyltics or something? This way even though people so sign up for free you'll gain a bit of knowledge about which package they clicked on and as a side effect the potential intend. Not perfect but better then no metrics.
Been doing that for years...