I just pooped out $500 for Sonar Platinum and think it's completely ridiculous that I have to shell out more money for the ability to export in mp3.  Can someone please point me towards the exact items I must BUY to get this working.
 
Thanks.

I believe this feature must be sold separately due to a licensing issue. This topic seems to pop up once in a while because it is frustrating and hard to understand. There are currently two options in the store and I'm not sure which one you need to buy. They're both $9.99. Here are the links:
Cakewalk MP3 Activation
Cakewalk MP3 Encoder Download
Perhaps someone here can explain the difference. I bought this option many years ago and can't remember which is the right one.

rubbish, eh?
best use LAME for free  then http://forum.cakewalk.com/TUTORIAL-Getting-LAME-MP3-Encoder-to-Work-With-SONAR-m1255631.aspx

TBH, forget the encoder in Sonar. It's okay, but average at best. THe system I use is to export to broadcast wav and then create all my MP3's in Audacity. It is free and also comes with great tools for tweaking tracks.
 
Plus Sonar MP3 takes "forever" to create MP3's - Audacity takes about 4-5 seconds.

Here is an image of the two mp3 products sold by Cakewalk side-by-side http://forum.cakewalk.com/FindPost/3273106
 
The correct product to purchase is the Cakewalk MP3 Activation. This program unlocks the encoder integrated into current Cakewalk products. As others have mentioned there are alternatives and there is no requirement to purchase an mp3 license from Cakewalk.
 
The Cakewalk MP3 Encoder Download is for older products and does not work for current Cakewalk products.

joden
TBH, forget the encoder in Sonar. It's okay, but average at best. THe system I use is to export to broadcast wav and then create all my MP3's in Audacity. It is free and also comes with great tools for tweaking tracks.
 
Plus Sonar MP3 takes "forever" to create MP3's - Audacity takes about 4-5 seconds.

+1, also an external wav editor allows for quick edits prior to the conversion.

I think there is enough people who have requested this over the years cakewalk should had just have added it on, it does seen to wind people up they have to pay extra 

Use lame.

Although Lame installation and configuration is something kind of boring and laborious, after this work, it works perfectly.

+1 for the LAME route