You should correct your statement to "we only pay what we feel is a fair price for a player we need" which would be every club's mandate. And most club's know that high end talent costs a premium.
This seems like Adelaides philosophy, as they haven't really bought in many players that were best 22 locks at the clubs they were departing. Their list from recent years is lowden, cheney, menzel, seedsman, hampton, gore.
Now there's nothing wrong with trading for players who can't make their current teams 22, but you obviously pay less as the club losing the player usually deems them surplus to needs and puts them on the table.
If menzel is worth pick 28 and kerridge, and seedsman and hampton are worth picks in the early 30s, then surely Gibbs (likely top 3 midfielder in the crows lineup as it currently stands) is worth more than picks 13 and a pick in the 50s. Compound this with the fact that he still had a long term deal, so there was no pressure to trade and you get the outcome we had.