The ebook industry differs from your preferences, selling ebooks for about the same as the hardcopy. The proposed price is well below the MSRP of $50 but you're still not satisfied, comparing it to the discounted price, and then saying even that is 50% too high for you.
How can we in one breath argue WOTC needs to get with the times with ebooks, and in another say they need to trailblaze well against the times with their pricing for that same product?
Comparing the regular ebook market with gaming ebooks is apples and pears: they're not quite as different as oranges and seems identical on the surface, but the similarities are mostly superficial.
Regular ebooks tend to have two prices: equivalent to hardcover and equivalent to paperback. The price drops from the former to the latter as the physical copy changes. Gaming books won't downgrade to paperback, so the price shouldn't change over time (unless they decide to put later books on "sale"). They don't need the initial high price for early readers to match the collector/book lover price.
Additionally, many people will buy a second copy of a gaming book as an ebook, which is far less likely to occur with novels or other ebooks; this means gaming ebooks need not be priced the same as if they were replacing physical sales.
And gaming books are likely to be shared amongst a table; one person tends to buys the physical book for the group. The PDF can act as an alternative reference source when not at the game. If priced the same as the physical book (or more) then there's no reason to buy the PDF, they'd just purchase their own copy of the book. Alternatively, for gamers who do not play in the same location as the gaming library (such as conventions or play in stores) the ebook provides portable access without carrying multiple heavy books.
However, unlike novels or other ebooks, gaming products will see also continuous use rather than a single consumption. So one could argue the price could be higher as the price-per-use will be low. But that doesn't offset the above.
Oh, and just because a related market is gouging their customers does not mean you have to gouge your customers. The price of ebooks and related digital media is pretty egregiously high, as you're not paying for the physical production costs. Selling PDFs, even through an intermediary who takes their cut, should reduce expenses by 2/5th to 3/5ths. I have some Print on Demand books on Amazon and the price I need to make the same profit on a physical book is significantly higher than the digital ($12 vs $4), and I'm not getting the discount of high production numbers.
High prices mean more profits per sale but fewer sales, while pricing low means more sales but less profit. I'm sure there's a sweet spot for PDF prices, where lost sales are balanced with high prices. But some serious market research would be needed for this and it likely varies from company to company and product type to product type. Hasbro/WotC likely has the resources to do so, but isn't likely to invest that time for a niche product like D&D.
I'm personally quite happy with Paizo's model. That's close to the industry standard.
They charge a low price for their hardcover books, the products where you're buying a secondary copy. The price ratio between physical and electronic varies if the product is one where you need a secondary copy versus a physical copy, with products such as adventures (not shared between people at the table or used by multiple people at the same time, potentially a reading experience and not a reference tool, less likely to regularly need two pages open at the same time, etc) are priced much higher. The campaign settings books, which are much more flavour than mechanics, are also priced high as PDFs. if you're buying a PDF copy of Dragons Revisited that likely is coming at the expense of a physical copy.
Now, for smaller game companies I can see things pricing differently. They need all the sales they can get just to break even and know that they're unlikely to sell both a digital and physical copy. They need to charge more just to recoup their production costs. So something like Numenera or 13th Age can go a little higher with their PDFs.
But that's not the case with WotC. They're making a profit off their printed books. They'll easily sell enough copies to pay for their production costs, so any PDF sales are a bonus.
Paying for a PDF is also often a courtesy for gaming books. If you own a physical copy you're within your legal rights to make a digital copy. That's covered by the same laws that let you put a CD you own onto your iPod. It's archiving. Like those video game emulator download sites.
Downloading a book you own falls in a legal grey area, and is basically skipping the slow process of scanning a book yourself. Which, frankly, is getting easier and easier since most phones have a camera capable of "scanning" a book pretty quickly. Geeks are pretty tech savvy and possess reasonable Google-Fu, so most can easily get ahold of a PDF if they want. You're paying for a PDF because you want to, so gaming PDFs have to be priced to move.
So far, almost nothing has slowed the piracy of D&D books. There's was a scan of the Monster Manual out before the book was available in non-WPN stores. As such, releasing official PDFs at the standard release date would arguably delay piracy as people would wait and then scrub a purchased copy (and WotC would make at *least* one sale for PDFs opposed to none). The only thing I've seen delay piracy was 5th Edition, which slowed the theft of 4e books as no one wanted to buy them.
WotC could also do things to boost their PDF sales. For Pathfinder organized play, to use an option you either need to have the book or a PDF with your name on it. A similar requirement could be required for D&D Adventurer's League, where you need the watermarked PDF (or book, or DungeonScape with your name). I have bought PDFs just so I can use content in PFS without needing to carry an extra book.