What's the catch with this WD 1TB SSD? Seems too cheap to be true

the catch is you can just buy an internal for 10$ cheaper.

The best $/TB for this form factor and performance category seems to be the Crucial X6 4TB, which Amazon and B&H have for $149 atm.

As it was mentioned, it's the normal prize now. Just check the prices next time for alternatives or check on a few sellers.

This is normal price