I definitly agree with the external hard drive.
Seagate 2TB If you actually trust seagate, this one is quite cheap on this weak sale. 80$
WD green 2tb I swear by WD drives, 90$ in sale. I use these for file storing, very fast drives for the price.
USB 3 enclosure42$ on sale.
Docking station (USB3) $30 on sale.
USB 3.0 enclosure 37$ on sale (27$ if you take the MIR into account).
So basicly, 2TB + enclosure ~~ 130$. You won't get that kind of price/GB ratio with Blu rays..
+ on a 2TB drive with USB3.0 you can have a decently fast storage solution, with retro compatibility with older PCs (USB2.0) and you can easily erase data from the HD. You don't need to swap dozens of discs while restoring TBs of data and on the long term, 1 external HD is less space consuming than 20x50GB blu rays or 40x25GB blu rays.