The confusion lies in the fact that we already give bonuses for the higher amounts of PC purchases on a normal basis. The flat conversion rate is $1 (or 10 kreds) = 6 pc. So for example, for the highest price point ($200 or 2000 kreds) if the flat rate applied you would get 1200 pc. (now obviously we do not do a flat rate under normal circumstance for that price point) The current sale gives up to a 45% bonus on purchases and in the case of the highest price point 45% of 1200 (the flat rate) is 540. So thus the bonus amount is 1740.
HOpe that helps make some more sense of it.