As an entrepreneur/programmer who makes a good living from writing and selling software,

You are not a programmer, at least not one sharing the scientific and engineering that makes most programmers choose their field. You are an entrepreneur who uses programming to make a living (not a bad thing by the way.)

I'm dumbfounded as to why developers write applications and then put them up on the Internet for free.

Sense of charity? Sharing? Common good will? Scientific and engineering desire to advance technology and knowledge?

You've found yourself in one of the most lucrative fields in the world.

Inconsequential, even for industries outside of software. How many companies, profitable in other fields, actively engage in charity and community support?

A business with 99% profit margin,

Only if you are working on the small, playing tax games or doing something under the table. The idea of a business that is that profitable, continuously and in a manner that is sustainable is not supported by the laws of economics.

where you have no physical product but can name your price;

You can only name your price when you

are dealing with a very desperate (and uninformed) client, you are a technical ace (say a MSEE specialized in RF and MW circuit design or FPGA programming or a very experienced software architect.)

Otherwise, no, you don't get to name your price because there are a lot of very capable people competing with you for contracts.

a business where you can ship a buggy product and the customer will still buy it.

And that's why you will never understand why programmers, scientists and engineering alikes (as opposed to money whores), do contribute to open source.

I would actually state that I doubt what it entails to have a successful, sustainable company, independently of the industry.

You ask Nike and they'll tell you they are in the business of making good shoes. They are not in the business of shipping a shitty product.

You ask Apple and they'll tell you they are in the business of combining the best technology with the most exquisite of user-experience aesthetics. They are not in the business of shipping shitty products.

You ask AstraZeneca and they'll tell you they are in the business of medical advancement, not on shipping a shitty product.

And those are not examples of empty rhetoric.

And so on and so on. And though it is always possible for defective products to be put on the market, all successful companies define themselves by a particular goal of excellence. Profit is a side-effect of it, and certainly the primary objective. But it is certainly not their primary drive that get things moving.

There is nothing greater than working in an environment like that. And there is nothing shittier than working with people who see profit as their main drive. Quality takes a dive completely.

You should do some reading on Warren Buffet's work or on Henry Ford's drive for quality and work ideology. Then you'll understand not only what open source is all about, but you might learn a bit or two about sustainable, successful businesses.

Entrepreneurs that don't understand that aren't really entrepreneurs. They are just peddlers riding a for-the-moment speculative wave.