Also, does Exchange Server come bundled with Windows Server 2012 R2 Std?
No it does not. I don't know if you were here for the mourning thread over the loss of SBS 2011 Std. It came bundled with Exchange and SharePoint. Exchange costs ~$1000 on its own. OEM SBS 2011 Std. versions are still available for ~$700.
Ouch. That *is* reason to mourn...
But Exchange and Sharepoint don't care who they're matched with? I could install them on Server 2011/2012 Essentials, correct?