This is a pretty open-ended question for multiple reasons.
- It is not possible to see all places on the planet in a lifetime, to be frank.
- You can travel like a king or like a backpacker – So, costs vary considerably
- How much time do you have for this trip? – Slower modes of transport and flexible schedules tend to be cheaper.
To be honest, you could actually go around the world in 20 odd days with 2-3k USD or spend a fortune and a lifetime and still be halfway across. It really depends on what you want the tour to include. It could vary vastly from someone interested in nature and wildlife to someone interested in history and architecture. It might be entirely different for someone interested in culture and cuisine.
I belong to nature and wildlife category and have the following on my bucket list, but have no clue about the costs involved. But, one thing I know for sure is that I cannot afford it as of now.
- Sikkim and north-east India
- Valley of Flowers in Uttarakhand
- Galapagos islands
- New Zealand
- Serengeti national park during the annual wildebeest migration
- Masai Mara
- Lake Nakuru during the wet season to see the flamingos
- Great Barrier Reef – snorkeling and scuba diving
- Rann of Kutch on full moon night
- Salar de Uyuni – The largest natural mirror in the salt pans of Bolivia
The best places in nature are usually the most difficult and expensive to get to. If you are more into history and architecture, most of Europe would be of interest to you.
Similarly, costs can vary vastly depending on what kind of facilities you expect from your accommodation and what mode of transport you prefer.
One of the good options is an around the world cruise that is offered by many cruise liners – but, be prepared to spend a lot of time sailing and be aware that you will only visit places that have ports. So, most countries that are inland would not be covered. But, you would definitely get a flavor of a world tour. Here is an example that costs around INR 1,000,000 per person and lasts for more than 100 days!