It means you could have done better in the negotiation, e.g., you bought for 10 what you could have had for 8. You "left 2 on the table".

leave (something) on the table v. phr. to refrain from taking the utmost advantage of something; to not address every aspect of a situation; in the form leave money on the table, to negotiate a deal that is less financially beneficial than is expected or possible. (Colloquial) http://www.doubletongued.org/index.php/dictionary/leave_something_on_the_table/ "Leaving money on the table" is a euphemism for losing a key point in a negotiation. But it's also a literal pitfall you must avoid in order to get the best possible salary. In a job-offer setting, we often tend to be weak negotiators, because we feel pressure when negotiating on our own behalf. This leads to leaving money on the table. http://hotjobs.yahoo.com/jobseeker/tools/ept/careerArticlesPost.html?post=24 Leaving Money on the Table(s): An Examination of Federal Income Tax Policy Towards Native Indian Tribes http://papers.ssrn.com/sol3/papers.cfm?abstract_id=1009221 By not writing application software for Linux platform, Microsoft is foolishly leaving the money on the table. They can make money out of growth of Linux if they just give in and write application software such as Office for Linux.

It probably comes from poker: 1) "If you hold a winning hand in poker yet fold your cards due to someone's bluff, the players call it "leaving money on the table", because you could have won the pot. In other words, had you played your cards right, the ones you already had in your hand, all of the money in the pot would be yours. Many manufacturers are "leaving money on the table" by failing to implement Lean Manufacturing principles in low labor rate areas. However, the really smart players utilize Lean to reduce their waste and maximize their profits." Source: http://continental-design.com/newsletters/lean-kaizen-takt.html 2) "Historically, IPOs both globally and in the US have been underpriced. The effect of underpricing an IPO is to generate additional interest in the stock when it first becomes publicly traded. This can lead to significant gains for investors who have been allocated shares of the IPO at the offering price. However, underpricing an IPO results in "money left on the table"—lost capital that could have been raised for the company had the stock been offered at a higher price." Source: http://en.wikipedia.org/wiki/Initial_public_offering 3) Further information: http://immania.com/general-im/dont-leave-money-on-the-table/ http://rharoldhollisantiques.blogspot.com/2007/10/leaving-money-on-table.html

10-4-2017 The phrase comes from roulette. If you leave money on the table you have placed a bet for the next turn.