Elon Musk has a ballpark assumption that allocating one-ton of mass is enough for the passenger, supplies, and luggage.

Improving the Cost Per Ton to Mars from $10 Billion $200,000

Elon sees the following key elements to lower the costs to Mars.

Most of the improvement would come from full reusability somewhere between 100 to 500 times cheaper. SpaceX already has made 70% of the Falcon 9 block 5 reusable. SpaceX is on the way to making a fully reusable Super Heavy Starship.