Yes, THROWAWAYS is a Scrabble word!

Letter values in Scrabble US: T 1, H 4, R 1, O 1, W 4, A 1, W 4, A 1, Y 4, S 1.

Is it a valid word?

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

(sometimes offensive) a homeless boy who has been abandoned and roams the streets
an advertisement (usually printed on a page or in a leaflet) intended for wide distribution
words spoken in a casual way with conscious under-emphasis

Also: street arab.