I think there is a lot of marketing going on, though I may not understand what you mean by “traditional”. Folks selling WordPress software do everything that larger players do: ads, cross-promotion, sales, events, affiliates, etc. WooCommerce, the most used ecommerce solution (based on the amount of WordPress sites that use it, which in turn have the largest segment of use) had a complete conference dedicated to it in the last year.
There are some freemium models, which follow shareware -> app store paradigm, and a lot of them show up in the official WP repo as “lite” versions of the pro plugins. But a lot of the standard go to plugins used by many developers do not have demos. They do their marketing like others.
I suppose it depends on who the user is. For instance, I buy a lot of software, and use it to build sites for clients. While they definitely benefit from it, it would be a stretch to say they “use” the software. In most cases I am the sole interface.
Now, for me, I greatly benefit. I can change the software, and I’ve submitted patches upstream to such packages. It seemed like the correct way to interact with the software, and I never thought about the commercial nature of the software. As I mentioned in person, what you are buying is support and ongoing updates. In a way I see this as crowdfunding a developer to fix a particular problem for me (with money coming from all the other paying customers).
There have been examples of what you’ve noted, case in point being WooCommerce, which started as a fork of another commerce plugin (or WordPress, which is a fork of b2, and really does the heavy lifting for all the other plugins ^_^). If one follows WordPress news/drama, every six months some asshat comes along and bundles a bunch of GPL software together and sales it was pennies of what one would pay if they bought it from all the folks that develop it. And it always ends with them getting a C&D from projects for trademark infringement and complaints from customers that tried to get a deal and end up with no support. Next time it happens I will post it here.
As a business, um, entity… meh, I work in the WordPress ecosystem, and run a business, so I also pay attention to how things are priced, and how these folks make money. It is fascinating when they break down the lifetime value of a customer that renews over many years, and where the price points come into play. It is something that I wish applied to other free software ecosystems, but I have a half-serious theory that WordPress is too mainstream for FOSS advocates to care about, and thus most free software is stuck begging for money.