I think your analogy is a bit extreme.
We're talking about a condenser mic that costs less than 200 bucks, and will deliver MUCH better results... not 4 thousand dollars.
Micing an
acoustic guitar (as you mentioned in your post) ain't gonna sound half as good with an SM 57 or 58 as it would with a Rode NT-1 or an AKG C3000.
You wanted good advice, and you got it.
You chose not to follow it.
Now you've got "three" dynamic mics with limited sound reproduction, instead of one good dynamic mic, and one good condenser mic.
SM's are good mics, for sure. But, guitars, cellos, flutes, congas, and vocals are gonna sound 10 times better with a condenser mic.
Sorry, but a month from now you'll be kicking yourself. Tape machine or digital, it doesn't matter. Your recordings will only be as good as what you put into it.
Read the post above this one...
...the Doc is a musical genius who knows what he's talkin' about...