if you have Spark, they only offer it as a hosted solution. That's the Spark side, not the RE side. The theory is that they work better together if both are hosted by BB. The alternative is they charge you a hefty chunk of change to add an extra layer to integrate them if you host yourself.
The biggest reason for the fee cut is they are trying to promote the hosting service. They go so far as to offer free RE hosting for a 3 year contract on Spark.
Keep in mind that hosting when it was released cost tens of thousands of dollars per year. Why they would then start to give it away would give me pause.
My biggest recommendation is really ask BB as many questions as you can. Also - paying the price they quote you is like paying the sticker price for a car.