Despite the fact that nearly every 500gb ssd is around £120 to £160, and will be for at least another quarter, this is a good price currently for the 850 evo.
Barring the 850 pro, this is probably the fastest sata 6gbits ssd out there, (the sandisk extreme can better it - but try finding one).
SAMSUNG EVO SSD SPECS
Capacities: 500 GB
Design: 2.5-inch 7mm
Interface: SATA3, SATA2, SATA
Included Cache: 512 MB
Sequential Read: 540 MB/s
Sequential Write: 520 MB/s
Random Read: 98K IOPS
Random Write: 90K IOPS
Power consumption (idle): 2 mW
Power consumption (read | write): 3.7 W | 4.4 W
Endurance (Terabytes written): 150 TB
It looked like a third party seller when originally posted but that was because Amazon were in the process of updating their site. It is now sold and fulfilled by Amazon.