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 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.

As a dynamic microphone, SM57 is only usable in the studio for certain kinds of vocals/instruments - the loud ones.

You wouldn't want to record an acoustic guitar ballad on it.