It’s not high. A Write Amplification of 2.43x is about normal for MLC SSDs normally used, perhaps even on the low side.
Mine (a SanDisk Extreme II 480GB like yours) has a write amplification of about 2.15x, but it’s mainly because I’ve made lots of sequential writes, which lower the write amplification over time. With smaller loads the write amplification can be as high as 4-4.5x in some circumstances, from what I’ve seen. During normal usage it’s about 3.0x. I’m using Windows 8.
SanDisk does not specify a guaranteed life time, but seeing that the media wearout indicator is based on a total amount of 3000 P/E cycles, with an average lifetime write amplification of 2.5x it would take about 600 terabytes of NAND writes to deplete the rated endurance. That’s a lot of writes and thus, one shouldn’t normally worry about them under normal (consumer / home) workloads.
When manufacturers specify a guaranteed endurance, they usually mean Host Writes, not NAND Writes. For consumer SSDs, it’s usually a very conservative value to deter business / enterprise users from using them in servers or heavy duty workstations.
