@elanthis: a good engine can cut down development time and cost significantly, but it cannot make things from thin air. An RPG with 150 monsters needs 150 monster models (plus animation, voice acting and scripting). If every model costs $2000(*) to develop, then you'll need $300000 no matter if you are using Unigine or Rage5 or (now-dead, sucky) Gamebryo.
It would also entail a large amount of risk, as you said. Game projects fail. Most of them fail. Sometimes it's because of money, sometimes it's because of bad business, but most of the time it's just because you can't actually guarantee a game will be fun.
There is no scientific formula behind making a good game. There's a ton of DONTs in the game design process, but very very few examples of things you can toss in that are guaranteed to make the game a success. You can't actually know if your game will be good until well after you've sunk time into building a good portion of it. At that point, if you find out your game isn't fun, you've got two choices: scrap a lot of your work and change directions, or scrap all of your work and start a new project.
Both of those happen a LOT. Most games are developed behind closed doors and the project isn't announced publicly until it's well along in development, so you rarely see it happening, but it does happen. Bioshock is one of my favorite examples, because they released their early design docs earlier this year for fun. The original game design was completely different than what Bioshock actually was. They started building the original design, realized it wasn't all that great, switched things up, and came out with one of the most highly acclaimed games in the last few years.
This is a problem for developers on a budget. Switching gears mid-development is costly. If you're trying to work on a fixed budget, you can easily end up in this situation with no way to actually afford doing what needs to be done. Overwhelming odds are the project just folds.
As a developer, that's a problem. Even if you're the best damn game programmer in the entire world, you can't guarantee that the rest of the team and the game design and even the market itself is going to allow your project to be a success. Working with the hope that your game will make millions and then pay off insanely risky. Seriously. Insane. As in, you'd have to be a crazy dumbass to go in for it.
Non-indie developers sometimes start up that way, but they expect to get funding within a few months. They get a few talented people together to basically throw together a game pitch demo, and then go find one of the big publishers to pay them to finish it. Which means that those developers are only working for peanuts for a couple months, not the 1-6 years it takes to release a modern AAA game. If you're a good developer, you can go find just as many well-funded interesting projects to work on as you can poorly-funded indie projects. The game industry is always hiring and there's a shortage of truly talented programmers and artists.
I really think you should revisit the movie metaphor. Indie movie makers can make some fantastic movies. I have some friends in the southeastern Michigan area who have done a few fun zombie flicks, a sci-fi post-apocalyptic flick (thank you Detroit for your dilapidated, crumbling buildings), and a few dramas. Good movies. Still, indie film makers will never, ever recreate something like the Lord of the Rings trilogy, Harry Potter, Fifth Element, Iron Man, etc. These just are not indie-class movies. It's not possible. Their budgets (even if you remove the "big name actor" paychecks) are in the hundreds of millions.
Another way to look at it: at some point though you have to realize that you can't get an Aston Martin for $50k and you're going to have to settle for a Mustang. Mustangs are still nice, sexy cars; but they're also still not the best of the best. That's just how it is.
Digolus very well may come out and may very well be a great game. As stated and with some of the assumptions people are making here, though, it's incredibly risky. And it's definitely absolutely not going to be of the same scale as the recent big-name RPGs.