It will add to the hassle but if times work out you can get flights from 65 to 85 $ each way to/from ST. Thomas on Jet Blue and then either Speedys ferry if right day or combination of two ferrys to get to VG. It would keep you under the 500$ budget if times work out..check SWA flights amd Jet Blues and the ferry schedule on BVI people talk here and see if works.