ReadyAPI Benefits in Load Performance Testing

What are the functional benefits of using the ReadyAPI? 

Does one have to upgrade to SOAP Pro before installing ReadyAPI?

What is the cost?

Most the Load Testing Docs eventually point to this plug-in, so I'm wondering if this is simply a sales pitch or are there sound benefits to purchasing it.

I'd be requesting it to be installed on a company server, so it's not an option to download a trial version.