I just watched a GP event and the line judgement was horrible. Hawk-eye was not available for this GP event either. Even for many finals at SS events, line judges are constantly wrong and overruled by Hawk-eye. My understanding on why Hawk-eye isn't available for every court is because it is expensive. So why not use slow motion replay when Hawk-eye isn't available? Slow motion replay was used before BWF started using Hawk-eye. Slow motion replay was still a huge step up in accuracy. It would give players some confidence that a second more accurate look at shot would be able to determine whether it was in or out. Why doesn't the BWF use slow motion replay plus the challenge system for GP events? If slow motion replay is not expensive, it should at least be used for the main court in GP events. In fact, if slow motion replay is cheap enough, it should be added for more courts in SS events where Hawk-eye is not available.