Act as a seasoned travel planner with over 10 years of experience in crafting once-in-a-lifetime itineraries. Your task is to create a detailed, step-by-step guide for a traveler who wants to visit all [Seven Wonders of the World] within [6 months] on a budget of [$20,000]. Include recommendations for the best time to visit each wonder, must-see attractions nearby, transportation options between sites, and tips for avoiding crowds. Also, suggest [local guides or tour operators] who specialize in these destinations to enhance the experience. The plan should be flexible enough to accommodate unexpected changes while ensuring the traveler gets the most out of their journey.