I generally hate hidden pricing and using products with it because it generally means the company attempts to charge whatever it can get away with and is afraid of having their clients find or what others are paying.
What I will say, however, is that it has been worth it. Whenever we need Basho's support, they are on the line and ready to help us. Their staff has been excellent to us and I couldn't be happier about our relationship with those folks.
Whether it is sitting down and talking to them about some what-if scenarios, discussing optimizing our usage, or even reviewing configuration files before we spin up a new cluster -- they've been on the ball. We recently renewed our contract for another year and I can't imagine us not doing that as long as we still use Riak.
Don't forget though, if you are in a startup, we have Riak for Startups (http://basho.com/products/riak-enterprise-for-startups/) where you pay what you can.
http://wiki.basho.com/Multi-Data-Center-Replication-Concepts...
I think Basho has a ops guy that is tasked specifically with going to these Enterprise companies and helping them with the setup - multi-site replication most likely means there are hundreds or thousands of nodes being deployed and that type of thing is really complex and also tricky to do right (even with Riak, which makes it REALLY easy).
My feeling on the price issue is this: Riak is willing to work with their clients - if you need it, you're going to call them and they basically workout what it is you need and what they can provide (maybe it is just the multi-site addon, maybe it's that plus a ops guy that knows Riak in and out and can get you completely set up worry-free with full-time support).
And, I think you'd be surprised. Multi-site replication is a requirement for companies and applications both large and small.