Don't think I've seen a deal on V4 lightstrips before, though prices definitely aren't as good as V3 yet.
Differences between V3 are addition of Bluetooth, there's a cut end connector included, and a smaller 6-pin connector see comparison.
One issue we noticed during product testing is that the solder contacts on the V4 lightstrip connectors are very delicate and easily prone to separation with excessive movement. We caution being very gentle during your project installations and take care to provide proper strain relief near the connector housings.
Another issue we noticed is that the resistors are very temperamental and prone to burnout in both the lightstrip and controller with any power fluctuations. We advise to connect and install our products only when the lightstrip has been powered off.