London to Geneva is about 425 nautical miles and roughly an hour and a half in the air. Every class of aircraft can fly it non-stop, and on a leg this short the fixed costs — ground handling at both ends and the operator’s minimum charge — are a large share of the total.
Private jet charter from London to Geneva starts from $9,000 on the smallest suitable aircraft. That is an indicative starting price, not a quote: the figure for your trip depends on which aircraft are available, where they are positioned and the date you fly.