I'm searching routes YVR-BKK on points in J class. I found an interesting routing (YVR-HND and HND-HKG on NH, HKG-BKK on TG). If I search for and add up those segments individually, total fees including YQ are about $140. However, when I "book" the same routing together, suddenly the fees are $355. I searched but couldn't find a definitive answer - I found one thread disucssing TG fees being higher, but I'm flying TG either way; there's also a mention of HKG affecting fees depending on whether it's a connection or an origin or destination point.

Anyone know why this is happening? This is a 250% increase.