Morelos was one of a number of big-money signings made by Pedro Caixinha at Rangers.
Morelos, 22, joined Rangers last summer from HJK Helsinki and impressed intermittently during his first season, scoring 18 goals in all competitions but missing golden chances against Old Firm rivals Celtic.
The Colombian forward is currently considered Rangers' first-choice centre-forward but has failed to score in the Gers first two competitive outings under Steven Gerrard, despite a 2-0 aggregate win over FK Shkupi.
Robson, who also played for Celtic and Aberdeen and is now a coach with Derek McInnes' side, joked that the talismanic striker could be earning the same amount as the entire Dons squad.
"We [Aberdeen] should be up there challenging for the cups," Robson said. "But we shouldn't be 15-20 points near Rangers with the budget they've got and the money they're spending.
"[Alfredo] Morelos is probably earning more money than out whole squad put together. There has to be a reality check as well, but, I think we've battled it out and split the Old Firm and we need to try and continue to do that."
The Gers have finished in third place for the last two seasons since regaining their Scottish Premiership status, with Aberdeen pipping them to second place.
However, the Light Blues will be confident of a second-place finish and even challenging Celtic this season, after hiring Steven Gerrard as manager and bringing in some top-quality, proven talent.
Morelos is expected to start despite the presence of new signing Umar Sadiq ahead of Thursday's Europa League clash against Croatian side Osijek.
Have something to tell us about this article?