I'm new to this business, so perhaps I'm wrong, but it seems that the primary purpose of the regular publishing houses is to prevent folks with crappy books from wasting their money publishing firewood. Given a best seller, dealing with the delay and cost and pain involved with dinosaur hoops seems silly.
At what skill and market levels do you think the literary agent to dino-publisher is the proper path?
Possibly you're asking whether it would be faster and less trouble to publish your own book than to seek an agent who will seek a publisher for you. Faster for sure. You can have your book out in a few months. Less trouble? There'll be more to do. If your book doesn't need any editing or proofreading, it'll still need a cover, which probably means a cover designer, and there's a printer. You'll want to get estimates from both, as rates differ wildly. Your book should have an ISBN number so you can get it on Amazon and other online bookstores. And a barcode.
If your book is fiction, you'll want to get it into bookstores. If the bookstores are willing to stock your book, just to put two copies into every B&N, Borders, Waldenbooks and Books-a-Million will require 4000 copies. That many you can probably get for about $2 each, depending on length (assuming it's paperback). So you're out 8 grand plus another grand for cover art and design plus whatever it costs to ship 4000 books from the printer to you. The good news is, the bookstores aren't willing to stock your book, so you can lower your print run from 4000 to 100. Much more affordable. Your friends and family will buy a few of those and the rest will fit nicely in your garage.
Now, if your book is nonfiction, you have a shot. If you are highly knowledgable about Dachschund raising, and you have access to those who are interested in Dachschunds, like they all subscribe to Dachschund Magazine, or there are web groups with thousands of Dachschund lovers, it's possible an advertisement will get your book onto the radar of those who would enjoy it. Or start a blog for Dachschund lovers. If people love it, they might buy your book. You won't sell nearly as many as a publisher would, but you don't need to, as you won't have to share the profits with bookstores and distributors or wholesalers. (You will, however, have to ship every book that gets ordered, which means boxing and labeling and taking to the post office. Or paying someone to do it. It's even more trouble than sending out query letters, unless you love that sort of thing.) In short, if you have a desirable book and a niche audience you can reach, it's possible to avoid losing money self-publishing.
Some self-published books have done well, but if your goal is to have your book read by the most people, or to make the most money, your best bet is a major publisher. If your goal is to hold a copy of a book you wrote in your hand ASAP, or if you've queried every publisher and agent and refuse to see the handwriting on the wall, self-publishing is highly recommended.