Just FYI, the command line I use for LAME is:
LAME -q 0 -d -b 128 -v -V 0 -k infile.wav outfile.mp3
This basically tells LAME to compress as much as it can without causing an audible difference in the sound, and to not go any lower than 128kbps, and to not throw away any frequency data. It results in MP3s that are, to my ears and speakers, perfectly CD quality. The resulting files range between 230 to 300kbps, depending on the complexity of the audio.
On preview, I noticed that other people have addressed this point. Oh well, I had fun typing it, so you can read it. 
Nearly every single .WAV file I have ever seen was PCM encoded, not mp3 compressed. Your statement is technically correct (in that wavs can be mp3 compressed) but it is missleading to say “WAVs and mp3’s are the same thing,” because any wav the average user will encounter will be PCM encoded.
To do a little math: A PCM .WAV file of CD audio (44.1 kHz, 16bits/sample) that is five minutes long is 25min60s/min*44.1e3 sample/s * 16bits/sample, which works out to: 50.46 megabytes.
If you were to compress this PCM audio using mp3 compression, lowest compression (resulting in larger files) available in most apps is 320 kiliobits/s, resulting in a file size of: 5min*60s/min * 320 kilobits/s *(1024)kilobits/bit, which works out to 11.7 megabytes.
11.7 (mp3) is significant smaller than the 50.46 for PCM.
I mean, yeah, you can either call the compressed file x.mp3 or x.wav, it’ll work either way, but anyone who is looking at x.wav is justified in assuming its PCM, and anyone looking at x.mp3 will certainly expect it to be compressed audio.
I understand where your coming from, but your statement could be taken as missleading.
askol
thanks all.
>> it is missleading to say “WAVs and mp3’s are the same thing,”
That’s why I never said it.
>> I mean, yeah, you can either call the compressed file x.mp3 or x.wav, it’ll work either way, but anyone who is looking at x.wav is justified in assuming its PCM, and anyone looking at x.mp3 will certainly expect it to be compressed audio.
You are missing the point. you can compress your files whichever way you want and whichever way is most convenient. I have certainly run into many compressed WAVs, in fact, all but the very smallest are compressed or they would be unmanageable over modems. WAV MP3 compressed files are a bit more effcicient than .MP3 for reasons I have explained. Both use the same codec but they are different formats.
Nope, what FDISK said is right - WAVs compressed with MPEG layer III are just MP3s wrapped in a WAV header/footer. All the ‘streaming information’ - the MP3 frame headers - is still present. Take one of these WAVs, snip off the first 70 or so bytes with a hex editor (up to the first frame header, FF FB 90 6C or similar), and you have an MP3.