there isn't that much additional fuel involved in bumping the payload up from a single serving soda to a family size 12 pack, is there?
For a retun trip to mars, the mass ratio is around 100 parts fuel for 1 part sample return. It scales pretty linearly. It doesn't matter that it spends most time coasting, you have to accelerate it to the same delta-v regardless of the mass.
When I think back to playing vast adventure games, like Below the Root, that amazingly fit on two sides of a 5.25" floppy, but the same game now would probably be written to take up a CD-ROM, even using the same graphics. Programmers have lost the need to optimize.
What's the difference between a computer salesman and a used car salesman? A used car salesman knows when he's lying.