Hello. I have read and understood your requirements, and I'll repeat them in order to clear any doubts: whoever visiting an specific page of your wordpress installation will see a google map, and will be able to click wherever he wants; after doing so, a popup will ask him to pay whatever was specified by the site admin, by entering his email to be used as his identification token. On the other hand, the site admin will be able to set (and change) the winner spot, and wherever he puts this spot, all spots chosen by users in a 10-feet radio will reveal.
If I'm right then I could deliver in 5 or less days, depending on any details you may want to discuss or change.
Greetings from Chile