United are absolutely right to stand firm over that valuation, because they are under no pressure to sell and Lukaku will continue to be an asset for as long as he stays, even if he isn't a starter.
Inter, then, are simply wasting their own time the longer they pursue this deal without meeting the asking price and the associated speculation (some of it accurate, some of it not) is now making the whole thing rather embarrassing for the Serie A club.
United agreed a £75m deal, rising to £90m with add-ons, plus the goodwill gesture of waiving a transfer fee for Wayne Rooney when Lukaku arrived from Everton in 2017. It is only natural for a club that has often undersold in the transfer market in the recent past to want that back.
Unlike Liverpool, who sold Dominic Solanke to Bournemouth for £19m in January after precisely one goal in 27 appearances, and Real Madrid, who have already raised around €130m this summer just by selling fringe players surplus to requirements, United haven't had a good record in offloading fringe assets.
The club lost money - around £15m - on Angel Di Maria in 12 months. Memphis Depay went to Lyon in 2017 for much less than he'd joined only 18 months earlier. Another club might have got much more than £7m for Javier Hernandez, while Rafael left for metaphorical peanuts.
Lukaku still has three years, plus the option of a fourth, left on his current contract. He is going nowhere unless United say he is, and it is refreshing for fans to see the club finally take a stand.
The idea that Man Utd should accept Inter’s offers for Lukaku because that’s what on the table is beyond me. They have a valuation, it’s not being met, they don’t actually need to sell. #MUFC— Jamie Spencer (@jamiespencer155) July 20, 2019
Even though the Belgian isn't expected to be a regular starter in 2019/20 – manager Ole Gunnar Solskjaer is grooming Marcus Rashford as the premier 'number nine' – his presence in the squad will still be important after he continued to score goals under similar circumstances last season.
Nobody could blame Lukaku for wanting to leave; any footballer wants to be first choice, while playing Serie A in particular has long been a personal ambition of his. But that isn't United's problem.
This was a player who scored off the bench against Bournemouth and Newcastle during last season's busy festive period, while he also netted braces in starts against Arsenal, Crystal Palace, Southampton and Paris Saint-Germain under Solskjaer, all important wins for the club.
Solskjaer is in no doubt over Lukaku's professionalism and ability, stating back in March, "We need to have him more in front of the goal, but he has done fantastic in his work rate, attitude, he loves scoring goals, he smiles every day, he does extra shooting in training."
But, United will let him go, if someone pays the asking price. It's very straightforward.
Inter are intent on getting him, with new coach Antonio Conte very keen to work with Lukaku after former club Chelsea failed to sign the striker ahead of United in 2017.
"I think frustrated is a big word," Conte lamented. "He is a United player. That is the reality. You know I like this player. I tried to bring him in Chelsea. Today Lukaku is a United player. At this moment we are talking about a player from another club. I consider him an important player for us to have a good improvement. At the same time, there is a market, we know our situation."
For all the talk, Inter simply haven't offered United an acceptable deal.
There were rumours about the 2010 Champions League winners proposing a two-year loan for just £9m, followed by an obligation to buy for £54m. There has been other gossip about players being offered in part-exchange, including Ivan Perisic, none of whom would interest United.
Either Inter cannot afford Lukaku and should move on, or they don't want to pay the asking price and should move on. Whatever the case, they should move on because this is a waste of time.
Inter barely qualified for the Champions League and Conte, brought in with hopes of finally toppling Juventus, hasn't been equipped with the players he needs. After struggling to get those he wanted at Chelsea, the Italian might have been hoping for different. So far it is the same.
Inter are not wasting United's time with over Lukaku. They are only wasting their own.