Sources close to the situation say that Blackstone (BX) repeatedly requested the concession, threatening to otherwise walk away from the table during the “go-shop” process. Dell’s (DELL) special committee eventually favored the move, believing that it would increase the odds of getting a superior offer.

But some on the special committee also thought it may require approval from Silver Lake and Michael Dell, who had offered in February to buy the company for $24.4 billion. After all, the winning bidder would be on the hook (albeit indirectly) for such payments.

Silver Lake agreed to the request, perhaps because expense reimbursement would be cheaper than defending legal accusations of impeding a competing bid. But Silver Lake added a twist, asking that its group also be reimbursed for sunk transaction costs (which would be in addition to the already agreed-upon termination fees, were it to lose the deal). It also asked that the ceiling for both agreements be $25 million. The special committee agreed.

Carl Icahn neither asked for, nor received, a similar deal.

Such reimbursement arrangements are unusual, but not unique. Occasionally they are contingent on the rival suitor (i.e., Blackstone) making a formal bid, but that is not the case here.

“If you’re trying to get a higher bid for a $24 billion or $25 billion company, offering up $25 million probably doesn’t seem like too steep a cost,” explains a private equity executive who isn’t involved in the Dell process.

Another buyout pro adds that private equity firms easily could bump up against the $25 million figure on such a complex transaction, after paying for accountants, lawyers and a third-party consulting study. He added: “It basically gives Blackstone extra time to make up its mind, without it costing them a dime. Free option.”

Spokesmen for The Blackstone Group, Silver Lake Partners and the Dell special committee declined to comment.

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