If you search the forum you will find lots of posts about the bank offers.
There are not any actual facts on how the bank system works,only ideas based on players experience.
and It would seem that you get better offers if you have a higher palace level and if you do not continuosly buy the cheap offers.
Maybe others will post again about their present experience ,because we know that the system changes, they add things and take things out, like troops for example.
EDIT
Often when people say my friend, they really mean me.
If you are really two different people, and you have seen the big gold offer. why not get your friend to do what you have done and see if that helps?