Almost every pricing mistake in this category is a state mistake: pricing a loose piece against boxed sales, or a crushed box against a clean one.
Four states
Sealed — never opened. Mint in box — opened, unplayed, box present. Complete, loose — all the pieces, no box. Played with — honest wear, possibly incomplete.
Put the state in the title. It is the first thing a buyer filters on, and it is the difference between the right bidders in your room and the wrong ones.
Then grade the box separately
A mint piece in a crushed box is not a mint listing. Say both.
Where to start
Loose and common: low start, fast pace, run them in lots. Good room-builders.
Boxed and sought-after: start sensibly, and set a reserve if a quiet night would hurt.
Sealed: fewer bidders, more questions, slower pace. Leave room for the questions.
Series and runs
Running a series across one show works. Collectors come for the one they need and stay for the rest, and the room learns your pricing as it goes.
Questions people ask
Does a reproduction part lower the price?
Yes, and hiding it lowers it a great deal more, later.
Should I split a set to sell?
Rarely for a matched set. Often for a pile of loose pieces where one is sought after.
Do I grade the box or the toy?
Both, separately, every time.