In my opinion, you absolutely must give people the chance to try your product. This means having a trial build on your website, which most Mac indies do but it's a bit problematic for paid apps, as I presume a lot of people on the MAS itself are unaware. It's in the best interest of everyone to have trials - for customers, so that they don't feel duped and actually buy a product they're happy with and for developers, so that they acquire real customers, not play a game of "can we convince people to fork over money without trying".
Moreover, it's in the best interest of customers to actually provide paid updates - they can vote with their wallet whether a business should survive. But without the proper availability of paid updates, customers are left with no choice, even if they did want to support developers. Unfortunately, the voice of a vocal minority instils fear in developers to try and charge for such updates.
Given the current climate, our plan for the future is to lower our initial price and offer major versions as paid updates. Instead of, say, charging $40 for the current version + $20 for an update, we'll just always charge $30 for the current version. As a side effect, it lowers the entry for everyone and your real customers can still vote with their wallets and support your efforts, if they choose to do so. One of the downsides is the introduction of a new SKU which is not that much of a problem (before the MAS, you had to do the same anyhow). It's usually wise to provide a way for customers to stay in touch with you and hear about updates but only if they want to (don't smack dialogs repeatedly in their face, that's just not nice).
I'm the author of the article in question, and with my current sales infrastructure, I'm able to spin up and sell a new product (SKU) in a matter of hours. Since I've been doing this for seven years, am I now overestimating the amount of work it takes to setup and sell your app independently?
As you say, you would ideally sell on both the MAS and outside. In terms of selling outside the MAS, it does come with some overhead, mostly related to VAT. Even worse, the EU is changing the VAT rules starting from 2015 (the rule change itself is designed to remove the competitive advantage of big companies to be based in EU states with low VAT and sell products in countries with high(er) rates):
> Currently, the place of taxation for digital services supplies is determined by your location as the supplier of the services. However, from 1 January 2015, the place of taxation will be determined by the location of the consumer.
It's not a big deal since you can just sign up for the VAT MOSS but it's still more hassle than just putting up an app on the MAS. Note that all of this applies after your exceed the VAT threshold, which is different in different EU member states.
[1] http://www.fastspring.com/pricing.php [2] http://www.hmrc.gov.uk/posmoss/
One interesting thing we have done, is offer a "lifetime upgrade" option for both upgrades and new purchases. About 30% of our customers buy it. It costs 50% more on a new purchase or 100% more if you're upgrading, but you get all future upgrades. It's a win for customers who want that, and it's definitely a win for us.
Interesting stats about the lifetime upgrades - thanks for providing those. I guess it works as long as all of your users don't buy it (which means your recurring revenue drops to 0 at some point and you're back to square one).