I lived about about a 1/2 mile from the interchange and although I am not 100% sure of the financing there was never any mention of BGW paying for any of the ramp work etc. The state very well may have paid for the ramp for 2 reasons.
1.The first is that the exit (243A, my apt. was off of 243B) also provides access to Hwy. 60, one of the major thoroughfares for Williamsburg.
2.The second is that there was a state interest to eliminate some of the congestion from I-64 and Hwy. 199 that was caused by BGW. I don't know how familiar any of you are with the peninsula but I-64 doesn't need much help getting backed up so the state might have been very willing to pony up for the new ramps. In such the state decided to reroute the entrance, not BGW.
That said, BGW did incur the costs of the road from where Hwy. 60 exits off, and setting up the new parking toll plaza.