Why do you need advertising for sales if you only have an alpha-version ?
It's honestly quite a long story, but putting it in the most simple way possible is that quite a bit of time and money is spent into this game, and it would be a large benefit to see some of it return preferably sooner then later. Not completely required, but definitely a large bonus. We definitely don't need to mass sell, but some profit will prove beneficial greatly, as you see, once we have a bit of profit then we can use said money to advertise. You may not be aware, and I truly don't mean to sound rude when I say this, but there are games out there which have Early Access. If you're unaware of this, you can find out more about it on Steam, or Desura.
I'm fully aware of that article, in fact it's one of the first things that popped up in my google search. A good read, but most of those ways consist of spending money, and those which aren't spending money revolves around asking family members, putting up posters, (which can be debated on how much it could cost, I most certainly know it wouldn't work in my area) or having some content already made in which you can provide in-game material. Putting it simply, the article actually expects the person to have a fully-created game. (or at least closely so)
One way to advertise an alpha game and get funds in return without coming across as selling an unfinished product is crowd funding (I assume you are familiar with Kickstarter?).
The problem is that crowd funding typically requires you to either have a stellar concept, or actual funds to do marketing (I realize that marketing an early alpha for the purpose of crowd funding sounds a bit silly, but its actually how a lot of people are getting their $ 25k - $ 49M (see Star Citizen if you don't believe this number).
Of course, one might argue that because this is now mainstream, its unlikely one would get much visibility from that...
Basically the last thing you said. However I have discussed this, and it's definitely a possibility. It's good advice, but unfortunately something I'm quite aware of. I know I may come off as ungrateful, and if I do I definitely don't mean it. If anything, I feel some regret believing that I already know most methods available.