The Resource Manager itself doesn't do that. We, at ExtraLicense.com (well, our addons), use Fetchapp.
Quite happy with it, check it out. You can then, from the Resource Manager, put a link to Fetchapp to purchase.
If you're selling add-ons, then most add-ons are < 100KB so I managed to get away with the free Fetch App service for a long time. I still could, in theory. But it became annoying having to constantly delete files before I could add new ones. So I pay $5. And I now have 23MB of storage remaining that I will probably take ages to fill up.
If you're selling large applications or styles then, yep, it could get costly.
But it does make me smile when I see people say $5 a month is expensive. At the end of the day, if you're selling something through that service, if you don't think you're going to make the $5 a month back then you might as well not bother selling at all!
If you're looking for a XenForo add-on that does it. Check out GoodForNothing Product Manager. I use it myself at http://xenmediagallery.com. I'm not a massive fan of it and the developer is AWOL at the moment. My desire eventually is to write my own. But until then it works fine.