The first reason it must be professional is that contrary to the saying 'don't judge a book by its cover' it doesn't really apply to actual books so the cover must be up to a high standard to make a sale, otherwise the person who may otherwise be interested in making a purchase will simply move on.
Secondly, there is usually no way you can browse a book on the Internet, the only thing your potential customers will see is the cover, if this isn't up to scratch these customers will just move on and look for a more professional looking book.
Furthermore, a professional cover means people are more likely to trust the things you say in the book and will be more likely to research around your existing products, increasing the chance of more sales considerably.
Another reason is if you have listed your cover on some of your existing websites and it is just a basic, boring cover they won't even think twice about clicking your link to purchase your book, they will simply disregard them and move on.
An eye catching cover will also catch peoples eye who are just simply browsing online book stores, if they are just whizzing through pages and pages of books with simple covers then the cover of your book will seem to explode out at them from the screen, this means they will at least check out what your book is about, raising the chance of a potential sale.
A further reason is that a professional book cover will tell the purchaser in seconds what the book contains and what they will be reading about, without a high quality cover people may get confused about what the book is about and while they may still make a purchase they may also ask for refunds or some other sort of compensation all because your simple book cover was not clear enough. I think by now you should realize the importance of a quality book cover, it is the cover which people will always return to.
Imagine two of the same books on Amazon, similar titles with exactly the same information in, one has a basic cover with just the title and barcodes etc. But the other has a fantastic cover with professional graphics and everything a high quality cover needs. Which would you buy?
