Sorry, but that's a terrible advice.
Let me illustrate.
A few years ago I developed a product (a software library) that I named "Elgrint". The name was carefully and painstakingly chosen, and integrated into the product so deeply that changing it would take a lot of effort and destroy backward compatibility.
I tried to buy the elgrint.com domain, but as in this case it was already taken by squatters who wanted $1700 for it. I got them down to $1100, but ultimately decided not to buy at all, and instead created a sub-domain on my main site (miranor.com), i.e. "elgrint.miranor.com", which costed me nothing.
It turned out to be a very good idea, because the product was a dead end regardless of the domain name.
Has I "invested" $1100 into a useless domain (and counting, since I'd have to pay for renewals too, possibly for the rest of my life), I'd feel pretty silly. And I'm pretty sure I wouldn't be able to resell it, because even after all these years this domain is still for sale, despite the fact that its owners are actually trying to sell it - something I wouldn't want to waste my time on, and despite the fact that it's a kick-ass name.
Now, if, against all odds, my product would've been a success, then I'd consider buying the elgrint.com domain. Yes, there would've been a chance that the price could get higher, but I'm pretty sure that it would've still been relatively small, because the squatters do want to sell the domain, so they wouldn't ask more than you can afford painlessly, as long as you negotiate the deal well and don't act like it's so important to you.
And you truly have no reason to act like that, because nowadays the domain name isn't as important as it once was. In ancient times (2010 and earlier) people did try to guess the company's web address from its name, but then all major browsers had merged the address bar with the search engine, so not many people guess addresses anymore - it's easier and faster to write the company's name and click the first search result. Most visitors wouldn't care about your domain name and many won't even notice it.
So your real goal should be the SEO - to make yourself the top Google result, whatever your domain is.