This is because there is mistake in ’tag bills’ function, the bill that you select is using the base tender bill, so the rate will sync in between. Thus, you have to make sure there is difference bill tag in each option, for example pictures below show difference bill for difference option.
If you wish to have different price within the same bill, you may click ‘export backup’ and import again for that particular bill and change the name for each option.
For clearly, you may refer to the tutorial,
tender option<https://youtu.be/9KJN14Llsr0?si=XXNqtxRMwdjR3Dby>,
export and import backup <https://youtu.be/EAx9jQDv-ck >.