When it comes to publishing, there are many mediums to choose from, starting with long or short in one direction (up and down?) and continuing to print or online in a perpendicular direction (across?). The mediums you choose to write and publish in will, to some extent, determine your audience. While there is a significant population of readers that reads both print and digital books, there are still plenty of people without the technology to read digital books and there are others who simply prefer print books; on the other hand, there are plenty of people who prefer digital books and there are others who lack the space to store print books. If you fail to provide one option or the other, you are cutting people out of your possible reading audience.
On the other hand, there is a cost (either time, money, or both) for providing print books and for providing e-books. The more significant that cost is, the more that cost must be weighed against the marketing impact a particular medium is likely to have. Another consideration, however, is the likelihood that a reader will prefer both mediums and will want a version of each, so there’s that to consider as well.
In the minds of many, considering the marketing factors when choosing the medium(s) you publish in is the same as factoring in the business decisions and that’s where they stop. Sadly, they’re wrong. As you will see, it’s much more complicated than that.
Imagine, for example, that you are publishing a novel. Novel readers—most especially Indie novel readers—are a flexible bunch. Some gravitate towards print books. Others gravitate towards digital books. But most won’t be so picky that they don’t get a book because it’s not available in their preferred format. There is a wide circle of very passionate readers out there, but there is also a lot of competition for those readers. Chances are that one or both mediums can be profitable if enough attention is paid to one’s marketing, though there is no guarantee that profits will be substantial. (Remember, revenues – costs = profit, so all you need to produce is a profitable book is to sell enough copies at a high enough price to cover your costs and leave some left over.)
If, on the other hand, you are publishing a nonfiction book, particularly a resource guide readers will want to refer back to, then you’re likely to find that people are more particular about the format they want. Some insist on print books. Others insist on digital books. But the important point is that they are not likely to buy the book if it is not available in the desired format, because there is probably a competing book that is available in the format they want. Failing to provide the medium preferred by your audience can seriously damage your profits, including your future profits on subsequent titles.
So, when you are choosing a medium, you have to weigh the marketing factors (how your decision will impact the audience you are trying to reach) against the business factors (how much you can reasonably afford to invest in your book). In the greater scheme of your business, all marketing decisions are business decisions, but not all business decisions are marketing decisions. Marketing only concerns itself with cost on two points: 1) how much cost must be incurred to reach the desired sales volume and 2) when does more expense fail to garner an increase in sales. Marketing, as a field, cares nothing for your budget; business operations do. The question for you, with regards to medium, is which one wins.