The best place to check value on a hubset like this that trades a lot is sold listings on ebay.
EDIT: found one HiLo sale @ $168.50 (rear only)

The year is usually easily determined by unscrewing the hub lock nut and looking on the inside surface. (Changed to the outside sometime in the 80's). Based upon the skewers, anyway, those will be '78 or later.

EDIT: Oops, I didn't catch that these were HiLo's. Accrding to velobase, those were early 80's. Your date code may be visible on the outside of the locknut.

Actual final value will depend on the quality of the bearing surfaces inside the hub, spoke hole distortions, as well as a clean outer appearance. Those give an appearance of being laced up twice already.