John Grisham said in the preface of one his latest books (Ford County).
... I discovered that selling books was much harder then writing them...
Same holds true for selling maps.
It's such a funny thing (the word "funny" being used loosely, in this context). People with a particular skill looking at sales and marketing (and the people who do it) as almost a necessary "evil" ...with sales people often treating the talent (map illustrators, in this particular instance) as "the help." A means to a financial end.
The truth is that illustrating maps and effectively selling our products and services are both arts in their own right. And if we're really good at one, but not good at the other (or at least not wise enough to admit our limitations and find/hire people to do the "really good" that we aren't as good at on our behalf), we'll always underwhelm when it comes to financial compensation.
The biggest disservice people in my undergraduate graphic design program were taught (which I sense is very similar related to cartography in the classroom) is the concept of
"if you build it (well), they (sales) will come." While developing great maps/illustrations definitely gives you much better odds of success, it doesn't mean much (financially) if folks have little/no idea how to package/brand and sell it.
So how this ties into the topic at-hand?!
1. Is the product being developed actually meeting a demand that exists in the marketplace? Not whether some people will think it is WAY COOL and want a copy for their wall/office! That will always be true. But rather, whether enough people are willing to plunk-down their money to buy a copy...and whether you are able to charge enough per-copy to make your net ROI worth the effort. If I had $1 for every time someone approached me with their "$1 million idea" (usually creating a map of their community, from which they envision selling ads to pay for the design costs, printing costs, etc.) who hadn't bothered to even craft a business/marketing plan or research competing products/alternatives, I'd be retired by now.
2. Getting the most bang for your marketing buck. Tracking the revenues and expenses tied to particular sales activities. It's not the news people want, but the net ROI of sitting behind a table/booth and selling maps isn't even 1/10 as profitable as investing that time/$$$ into a strong web presence. A great social networking presence (Facebook, blogs, ???). I agree 100000% with Jean-Louis that it's something that needs to be done from time to time to "disconnect" from cyberspace and remember what a handshake and a face-to-face conversation feels like!

However, that said, you won't make nearly the per-hour ROI for your investment doing those types of things vs. having a really good/smart business plan and electronic marketing initiatives.
3. Re-Read #1. 
I would love nothing more than to hire one of our talented team members to produce an absolutely stunning, award-winning map illustration of our local community! Only one
TINY problem: We're a town of 2,200 people (and aging/shrinking), and what I would need to charge residents, business owners, and former residents per-map to have a beautiful illustration hanging in their living room or office (just to break even on what I'd have to pay for the illustration and printing) would have them choosing between the illustration or buying groceries this week. Unless I'm writing off thousands in losses...which makes complete business sense?! Or not.
I wish I was wealthy enough to just draw whatever I wanted to draw (or hire people far more talented then I am to draw it for me). But until that day comes, probably around 3350 A.D. (lol), we've got to produce what we know can/will sell. And that means either contract work (being paid X to deliver Y for a particular project/client), or having someone immensely talented/experienced (like Jean-Louis) coaching/guiding us on how to SELL it. Drawing it?! We've got at least 5-6 people in our shop who can do it. Selling it? We've got one...and maybe a second person (me) if Jean-Louis is willing to be my
Sensei on all-things ad-mapping.

Do they teach any sales/marketing concepts in Cartography programs out there...or is it
"if you build it, they will come?" Which is about the equivalent to the business plan employed by the Underpants Gnomes in the TV Show
South Park:

1. Collect Underpants.
2. ??????
3.
BIG profits!
Of course, those gnomes are then innocently asked "what's step 2?" And they have no idea. As is the case with most people who want to produce and sell a product/service...but don't use due-diligence to actually figure out if they've got enough of a market and potential sources of revenue to off-set all of the development time, printing costs, sales/advertising costs, taxes, misc. overhead costs, et al.
I'll be quiet now...I promise! I could talk marketing all day/night though...I love it.