Since when the event first appeared in 2.0 the price have been 20 coupons per sack and is the reason why everybody has always thought this event was extremely horrible (exactly because everything there was too expensive) and only meant to be a heavy whale event for those that go for xserver top rewards.

I don't know if last month the sacks costed 10 coupon (didn't bother to check because there was nothing there i needed), but, if is so, then was indeed an unintended change brought by 5.0 because for the previous 14/15 months they always costed 20 coupons.

I play since almost two years, i know what i say.

The only change this event had during the whole 3.0 and 4.0 was in the drop rate of items in the sacks. Before 4.0 the average was 6/7 points every 5 sacks, after 4.0 (or in late 3.0, don't remember exactly when), was increased to the current 9/10 every 5 sacks.

It was not. The one with Killer Bee was indeed 10 coupons but the event originally started at 20 coupons/foodsack.