British Airways, Finnair, and Iberia have round-trip flights from Houston (IAH) to Mykonos (JMK) for $655-$669 with a connection. Flights August to September. Departures on Monday and Tuesday. 7-day minimum stay required. Fare requires an overnight stopover in London on the return leg of the trip.
Note: Avoid flying into and out of two different airports (eg: LON/LHR). The best routing is via LHR both ways.