Wasps announced on Tuesday they had completed a deal to re-sign the England fly-half from the Sharks for next season.
The move will take the 28-year-old, who has exercised a release clause in his Sharks contract, back to the club where he made his name six years after leaving.
Sharks director of rugby Diamond has taken a pragmatic view on the matter, but is surprised at Wasps' willingness to splash out on a player they do not appear to need.
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Diamond said: "There is an inflation in rugby across the board with the media values coming into it - BT are putting huge amounts in.
"Wasps are sat with three players in the same position of similar ability - Danny Cipriani being one, (Ruaridh) Jackson two and Jimmy Gopperth. What they are going to do with three players I don't know.
"We don't run that model. We run a successful business that has very little debt, if any, and is breaking even.
"For us it is about the whole picture and we have been highly competitive here for the last six years that I have been here.
"Players come and players go. Danny is a big name, but no doubt we will replace him with an equal."
Reports have claimed Cipriani will be paid around £400,000 per year by Coventry-based Wasps, but Diamond is confident money was not the player's motivation and has no issues with his decision.
He said: "It wasn't down to money, it was about him wanting to go further south, wanting to play with the guys he grew up with and, as he announced yesterday, 'once a Wasp, always a Wasp'.
"It's not a complete surprise. It happens. People move on. He has been a great asset to us on and off the field and we will look to replace him now.
"We had been discussing it, knowing that he had the clause in his contract, but he has finally made his mind up and we had to put a bit of pressure on him for that, because we need to know where we are as a club."
Diamond says Sale, who are seventh in the Aviva Premiership, will waste no time in looking for a replacement.
He said: "We start immediately. We will look around the world.
"We have not got anybody in the academy in that position suitable to come through at the moment so we will look further afield.
"Our first option will be to go English and see what we can find if there are any, but if not we will look internationally."
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