Agree to disagree. You're making a point about age, comparing 2 players with very different ages.
Gana is at peak re-sale age right now, will only get worse after he turns 30 and that is a fact. A player bought for £8million, selling at peak re-sale value can easily be described as a 'no brainer' although I personally think he would be very hard to replace, and would rather keep him.
Whereas if Gomes signed for 30m and had a great season, at the age of 26 next year he could sell/be worth 50m+ easy. Even if he was just a steady performer for 3 or 4 years, you would get the money back if sold on.