Yep, the Banker can offer whatever he wants. On the other end of the spectrum, he would've offered Eugenia £26,000 on a £100/£250k finish as she was so reluctant to risk any significant sum for the charity that she was playing for (i.e. she SUPER reluctantly said No Deal to £4,000 on a 7 blues/20k/35k/50k/250k 11 box!). In the past, the Banker also went to even to an even greater extreme by offering Alice a £17,500 Banker's Gamble on a 1p/£250k finish. Also, if Iris (1) went the other way at 3 box I am all but certain the Banker would've hypothetically offered £11,500 on a £5/£250k finish (as the Banker claimed earlier in the game that he won't bother offering more than that as he knew that Iris would deal at that regardless of the circumstances).