I think the key point is that we are charged both BL fee and switch BL charge, normally we are charged by only one BL fee around 1500-1700 by having 3 sets of BL. Even if one set of BL fee is 1700, then 3 sets of BL should be 1700x3=5100 but now we have to pay 1700+7240=8940.
The costs are strangely high. That is why we are wondering about what the switch BL charge means. Please kindly check and let me know
Many thanks
Penny