I think you are misinterpreting what you can actually do here.
First, there is not "InfoPath Server" (at least not by that name). You are perhaps referring to SharePoint 2007 wherein you can set up InfoPath forms to be delivered as browser forms. I don't know what that costs, but I'm sure it's not inexpensive.
Second, an MSI will not eliminate the need for InfoPath--though I have made several requests to Microsoft to eventually create fully executable forms (which it sounds like what you are expecting). However, the reality is that full executable forms will likely not be a reality for a good number of years if they create that feature at all. No, creating an MSI for an InfoPath form is a way to create a form that is installed on the the computer so that it can have "full trust" security. That means, your users will STILL need to have InfoPath installed, but if they installed your MSI, your form could do more stuff, because it is a trusted form.
As to whether you need VS Pro to create an MSI from InfoPath 2007 -- I don't know about that. I thought IP07 handled it all internally--though I've never really researched that, so you might be right.
Anyway, sorry to disappoint you, but in your scenario, you'll either need SPFS (SharePoint Form Services) to allow for browser based forms, or you'll need users to have InfoPath installed, or create a kiosk where they can go to use the form, or a server they can remote into and use the form that way.