"I just touched base with Joe Silva and he explained this is basically what happened regarding Mousasi:"
"Mousasi called him Saturday because he suspected he had been lied to by his manager, Appy Echteld, regarding an offer of $40,000/$40,000 from the UFC and then encouraged to accept an offer from Strikeforce. According to what Mousasi shared, that amount was less than half of the purse agreement he had with Affliction but he trusted his manager and signed with Strikeforce. The UFC would have honored the Affliction deal of $125,000 purse plus win bonus had Mousasi signed with them."
"Contrary to the claim made today by M-1 that Mousasi was on the phone during negotiations with Joe Silva for his services, Joe adamantly denies that is true. Had that been the case, there would have been no reason for Mousasi to call Joe to question Echteld’s claim of a $40,000/$40,000 offer from the UFC."
[UPDATE] Carmichael Dave post's the official story on the Sherdog forums:
"So the 40/40 figure was obviously erroneous, right?"
"Not only did we not make an offer, but we would’ve assumed his Affliction contract and its terms. So whatever Affliction was paying him, that’s what we would’ve honored, and it was considerably more than 40/40," Joe Silva said."
Editorial Note by Brent Brookhouse: Bottom line: M-1 lied to Mousasi to get him to sign a deal they wanted him to sign. They looked out for their own interests instead of his. They violated their duty to the client. The fact that Joe said they didn't make an offer is actually worse. It means that rather than lying about the numbers offered they cut off any potential negotiations by claiming a poor offer was made before the UFC had a chance to establish a starting point for negotiations.