Hello

I've just booked some tickets to Las Vegas for me and 3 friends. We are all different levels in the Executive Club, which made this a bit interesting.

So from what I read on BA.com, this is how Avios is rewarded:

Blue: Collecting at normal pace.
Bronze: 25% bonus Avios
Silver: 50% bonus Avios
Gold: 100% bonus Avios

The trip we have booked is a roundtrip OSL-LHR-LAS

What is interesting is that I would think that the Gold member would get double the points of the Blue member, but this is not how it is.

Blue: 19,282 Avios
Bronze: 22,256 Avios
Silver: 25,228 Avios
Gold: 31,172 Avios

Can someone tell me how this is calculated, and explain how 25/50/100% extra Avios does not give more than 15,42/30,84/61,66% extra Aviso than what the Blue member gets?

(I could not upload a picture since I'm a new member, so I just wrote down the points given)