If you do buy a blu ray player for your rig you will also need to buy some pretty pricey software to play it not to mention a compatible GPU. Also, I'd be very careful about buying the cheapest of anything as a rule.
Most of the Blue Ray players come with free software. The cheapest is best in the CD/DVD burners because they are constantly fluctuating in price. A few days ago one that was $25 (about the average price) is now $18 thus a better deal for the same quality product. I've gotten many through this theology and have yet to have one go bad. Lastly almost every new GPU can support Blue Ray playback.