1
general::
Compromise between two close figures, divide the remainder equally. For example, You're asking $5,000 for the car and I'm offering $4,000; let's split the difference and make it $4,500. [c. 1700]
American Heritage Idioms
2
general::
Phrase(s): split the difference
to divide the difference evenly (with someone else). • You want to sell for $120, and I want to buy for $100. Let’s split the difference and close the deal at $110. • I don’t want to split the difference. I want $120.
McGrawhill's American Idioms And Phrasal Verbs