To which I replied:
Well, an SM58 and any condenser mic are very different beasts in terms of proximity effect, etc, but yes, sonically - if used right - a cheap SM58 can be the BEST mic for someone - Aretha Franklin used an even cheaper SM57 on several of her biggest hits while vintage Neumanns sat in the studio unused!
Speaking as someone who owns several mics valued at over $5000 each, you might be surprised to hear that I agree with Eric on this subject. I have no problem at all letting my $8000 modified Neumann SM69 sit next to a $100 mic that might capture a certain vocalist better. So why have an $8000 mic? Well, there are other uses for these instruments - this is the one I use to record orchestras and such things with and it definitely shines in this area. For vocals, it is VERY nice, but the differences are smaller when used close-up.
How a mic captures sounds in an acoustic space is where you really hear major differences, but for the most part, we are recording vocals from 3 to 6 inches away and a lot of these factors are removed. I won't say it makes NO difference, but the differences are usually nth degrees, especially when there are a lot of tracks involved to make it harder to follow individual tones or sounds.
The most important part of this signal chain is the stuff on either end of the equipment itself - the performer's instrument and expression, then the engineer and/or producer's ears and their musical/mental/social ability to get the best performance out of them.
If a great violinist uses a Two Million dollar Stradivarius or a "cheap" $80,000 violin, can you tell the difference? Most of us can't, there are very few that can, but for the most part it's going to be about the performance (and it probably gives the player inspiration that they are using such an instrument.)
Now give the Strad to a 10-year-old violin student and give the student's $100 violin to the concertmaster and you'd probably rather hear the $100 violin over the $2,000,000 violin.
We're only going to be as strong as our weakest link, and if there are a handful of "decent, but not earthshaking" singers in your group (as most groups have), those nth degrees are not usually worth the price. Much better to have someone who actually knows how to get a better performance out of them, then use skillful editing as well as the other "evil things" such as AutoTune to make the final product sound better.
That being said, I'll also say for the record that I myself love microphones, and the character differences between the instruments. I've worked with them for many years, know them well, but that doesn't mean you have to. It's like an artist who can tell the differences between to nearly identical shades of blue - if they aren't right next to each other, we'd never know the difference, but it is important to that particular artist. If it's important to you that you have that whole palette available to you, then by all means go to a $1,000,000+ studio and pay the money to do so. The down side is that you'll have to do it much faster to keep hourly costs down. As for me, I'd much rather mix something recorded with care, love, and attention to detail than something that used an expensive signal chain.