I'm afraid this is most likely because You don't own the champion/champions. Notice that it says on the lower part "Offers include champion if unowned", so it adds the value of the champions in RP, in addition to the RP value of the skins.
Let's Take General Wukong's offer, for example:
The Skin normally is worth 750 RP;
Wukong on the other hand is worth 880 RP.
For a total of 1630 RP. This amount is discounted by -70%, which leaves it at 489 RP.
IF you were to own Wukong beforehand, then the price would be 750 RP reduced to 30% of the original cost, which would be 225 Riot Points.
Note that this happens because usually you don't own the skin without owning the champion first. The only exception for this would be getting granted the skin due to certain circumstances, like Victorious Skins which are granted once the season ends, along with the champion if you don't own it.
TL;DR: Don't worry, Riot isn't scamming anyone on this case. Just get the champion first for BE if you wish to lower down the cost on RP.