Exactly. After a certain point, you get diminishing returns. $100 gets you probably 85-90% of the way there, which is certainly more than enough. People forget that a good mic and a good DAW do not fix a bad take. The price of the tools is less important than their proper usage, and simply recording things well.
You don't even need an SM57. I know for a fact the iPhone mic and iPhone Garageband has been one artist's success.
The SM57 is a great mic in some situations. A lot of situations even. But saying that an artist can use an SM57 or an iPhone mic on a hit record and is sufficient is missing the point.
Steven Soderbergh has shot several feature films on an iPhone and the movies were still great, but they're nowhere close to unlocking the full potential of visual expression that you'd get with more refined tools.
Artists who are serious about their craft will keep an SM57 and an iPhone mic in their color palette (Frank Ocean comes to mind), but that's all they are for serious practitioners: a creative choice.
The SM57 is a workhorse of a mic. It's great in a pinch and probably a desert island choice. It's earned it's classic status for a reason and is probably on more records and stages in the last 40 years than anything else. Great mic... to a point.
That said, the ceiling of what's possible is far higher than what an SM57 can deliver. Not to diminish it. In some instances it's perfect, but one wouldn't have to look far to find better choices, depending on the context and needs of the record.
A Toyota Corolla (don't @ me, I'm not a car person) might be a low-cost, reliable choice in a pinch, but it's far from embodying what automobiles are capable of.
You don't even need an SM57. I know for a fact the iPhone mic and iPhone Garageband has been one artist's success.