If the goal is simply money, making it is not necessarily hard. There are many corporate positions that pay an obscene amount of money at the cost of being very dull. Somebody who enters a market with the goal of making money and nothing else is going to make a lot of money. Most of the routes available are much easier than the one that he picked, which requires a good idea and a lot of luck.
Alex was not slamming Sam's achievement. He just said that from a business perspective rather than a hacker's perspective, the hacker route to riches is very fraught and few people ever make it. You're an outlier, as is Sam, but statistically speaking, more people fail as hacker/entrepreneurs than fail as high-powered corporate lawyers or as cutthroat schmoozers. Even the moderate successes, like Sam (moderate being relative to, say, the people who created Facebook/Microsoft/Google), aren't particularly better-off than the people who merely submit to the system and work their asses off, so the risk doesn't pay a higher financial reward. The only reward is that of personal fulfillment.
-A Stranger in a Strange Land by Robert Heinlein
I don't like to think of hard in terms of the time required, but rather in terms of the skills needed and the things that need to happen to make the project a success. If you break down any project into a PERT chart, the best projects are the ones where each circle is capable of being realized in multiple ways. Whereas if you look at Sam's PERT chart, there are clearly a number of steps that are a one shot deal, where if they don't work the whole thing falls apart. For example if you can't partner with any carriers then the project is dead, unless you go around the carriers in which case your risk (and cost of capital) goes up so your upside goes down.
"What are the alternative ways of making $10m that you casually assume to exist?"
There are lots of ways. For example, doing LBOs on your own you can easily make 2-3 a year. The only problem is that you need the skills to know how to do this, and there are only a few hundred people at most who can serve as mentors to teach you at any given time. Running a fast food franchise is fairly predictable way to make 3-5m, so is starting a conference. If you start an ad network you can count on making 10+ if you know what you're doing.
There are tons of very predictable ways to make money on your own, the problem is they require skills that you can only acquire by finding a mentor who knows what they're doing. (And finding good mentors is a hard to acquire skill on its own.)
My explanation for why there aren't is that it's actually quite hard to make $10 million. Your explanation is that while it's easy if you know certain magic spells, there are only a few people willing to teach you these spells.
Please, honestly, don't plan your life based on this assumption. Assume it's hard to make lots of money, not that it's easy if you can somehow become an "insider."
For example, one can make money by getting 25,000 blog subscribers, using that to get a book deal, and using that to do consulting. It still takes an enormous amount of work, but at no step does it involve being chosen from on high.
edit: At any point if Scribd hadn't been able to add a zero to their traffic stats they could have leveraged their asset to do something slightly different. Loopt never had this luxury. If at any point they couldn't add a zero then the whole project was worth nothing. My point was that someone more experienced would have known this and chosen to start a business more like Scribd and less like Loopt. (If they only cared about the money.)
But someone competing with Loopt has different problem entirely. To even have a hope of competing, they have to make a deal with a carrier. And the number of available carriers drops as Loopt grabs more of them -- which gets easier with each one they get. When you're at the bottom trying to catch up, the fact that Loopt scaled a cliff instead of a foothill looks like a smart decision.
Take my blog -> book -> consulting example. Right now if you have 25k blog followers and you are willing to spend 50k out of pocket it's pretty easy to game the system to become an NYT bestseller for one week. If everyone did it then the the numbers needed would be higher, but right now the number of people willing to do the two prerequisite steps is low enough that this is about right. There is no point of failure; if your tribe isn't growing fast enough you can try a different blogging strategy, and even if your book doesn't make the bestseller list it still grows your tribe and makes it easier for your second book to become a bestseller. But the barrier to entry is still quite large because building a following sufficiently big is more work than most people are willing to do. Ramit Sethi did exactly this a couple months ago, and IIRC it took him ~18 months and thousands of hours. Huge corporations are never going to pay Ramit millions of dollars to teach them about personal finance, but it's easy to see how he could be making tons of money if he'd instead built an asset designed for that.
You have a good point that there are some advantages to Loopt's strategy. But even still, if you have the choice of starting any business in the world, why start one where you have to put up with that? Is the benefit of a higher barrier to entry really worth the risk it will fail entirely? Sure they have massive upside, but there are lots of other business with massive upside where you don't have to hope for a miracle.
It's like the steel business versus the soft drink business. It's really hard to succeed in soft drinks; if you're not Coke or Pepsi, you're kind of screwed. In steel, anyone can compete. Steel is just steel, so if you make a little more, or make it for a little less, nobody cares who you are or how long you've been in business. The steel business chews up capital with very low annual returns. For every dollar of tangible assets, Coca-Cola brings in $.75 in profit every year.
Because of this the only people with a big incentive to game the list anymore are people who want to use the credential to use consulting, so there is a lot less competition than there used to be. Of course new authors still try to game the list all the time for ego, but usually they do it half-heartedly so if you really have a permission asset in place and a good strategy its not that hard.