Social Media ROI and being realistic

ROI - Return on Investment.  I charge a client "x" per month to manage all aspects of their social media. I work very hard to make sure I'm giving good value for money, I don't switch off, I eat, breathe and sleep strategy and communication (with their audience) and I am  always looking for better ways to make sure I'm doing all I can... In short, the return on their investment in social media should be clear, right?

Leads generated via social media oriented destinations convert (sometimes, generally) to trackable website traffic which you then funnel to a sales transaction = Measurable ROI...

It's not that simple, though...

Why ROI isn't clear to me.

Let's say for a minute that your client is a camera bag manufacturer, that they have lots of users in the digital space, and by nature of digital photography, those people spend time on line. So "company a" invest in me to maintain their social communications - that's fine, so far... But, what happens if all of the people that I talk to, reply to, guide, chat with, laugh at or generally interact with over the course of my day, in relation to "company a's social media" then decide to offline it and buy company a's product via standard real world retail channels... (You remember shops, right?)

There's no way that I can track and report an offline sale - it's almost impossible to keep a "for sure" track on the online sales...

So, what if sales were up, everything looked normal, but there were NO conversions "via social" ....but really there are! (remember, they've gone to a shop to buy the product after they talked about it with me online!)

That's where I start to think - well, look... it's not really about ROI, is it? It's about building faith in your brand, it's about providing a good feedback channel and a secondary customer support line in.

Or do I have it all wrong? I'd love your thoughts below, please...

--Sime