Was this some sort of marketing gimmick that companies employed to familiarize and promote ebooks to people? Or are there other factors that result in this pricing?
There are three main factors why the price can be lower. One is transportation costs. The second is the 'cutting out the middleman'. The third is the cost of producing the physical book.
The physical transport costs and the need for human handling fall away if a book is transferred electronically. This is both the case when buying in a bookstore or from an online shop.
Physical books often go through distributors to stores and smaller online retailers. Ebooks cut out these distribution channels and their profits. Some publishers even have their own ebook sites, eliminating the profits of the ebook stores as well.
I hope the diminished cost of not having to kill and process a tree to make an ebook is clear.
I actually assume (but have no proof) that electronic books are artificially expensive compared to their physical counterparts, based on the percentages of physical book prices I have heard that authors receive.
There are lots of factors that influence a company's decision to make a ebook price lower.
The main reason would most likely be is an ebook doesn't require as much funds to produce as it does to produce a print book, thus resulting in the price being lower.
You could also say that since the demand is high and the quantity is very high (unlimited), this then results in the price being lower.