Even with the HDD industry's price gouging.. 500gb hard drives are around $60..
Plus, BDXL is only read/writable on a hand-ful of drives.. no blue ray vdeo players play bdxl standard unless clearly specified! BDXL is an EXTENSION of blue ray standard... which means old devices are not FORWARDS compatible to read the data..
Then again, dvd-rw wasn't widely available at the dawn of dvd media as well.. but you don't see makers rushing to apply these new extensions for fear of cannibalizing old on the shelf product. Makers of video players will circle the wagons for as long as they can..