I would think that it would be Ultegra for that money and as stated it would not be the full group set including crank and cassette,
Ui2 and Di2 are quire fussy with the quality of the cassette and can produce clunky shifting with non Ultegra / DuraAce cassettes so when buying components I think its important to consider if you simply want the consistency of electronic shifting or improve the quality and feel of your shifting.
Generally speaking Dura-Ace holds its value better than Ultegra as its interface is not dependent upon chipped components to be recognised in the system like the CANbus interface of Ultegra. This means that Ultegra is more difficult to hack and create custom shifting and battery solutions. Ultegra is also more difficult to troubleshoot when it goes wrong.
It is possible to obtain both Ultegra and DuraAce at really effective prices if you know where to look, but the reality is the whole group set is not cheap, if you find its cheap, its usually for a reason.. Be suspect of second hand electronic shifting and where possible ask to see it all connected and shifting. A dead shifter or mech could turn your bargain into a expensive buy imho.