Yes, STAPLE is a Scrabble word!

Letter values in Scrabble US: S 1, T 1, A 1, P 3, L 1, E 1.

Is it a valid word?

STAPLE is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

(usually plural) a necessary commodity for which demand is constant
a natural fiber (raw cotton, wool, hemp, flax) that can be twisted to form yarn
material suitable for manufacture or use or finishing
a short U-shaped wire nail for securing cables
paper fastener consisting of a short length of U-shaped wire that can fasten papers together

Also: staple fiber, staple fibre, raw material.