A lot depends upon condition, rust and engraved names lowers the value. Location also matters, same as buying/selling shop machinery. Different areas of the US will have different values for the same item. Age of the items makes a difference, if it's made in China (Starrett has been outsourcing for years) it's not the same quality as made in Athol (calipers for example). Lastly, the item itself matters, as examples:
1) Last Word indicators- Not very well regarded by most toolmakers because the movement gets "sticky" over time.
2 Planer Gauge- I've owned one for decades and have high regard for it but isn't used by many toolmakers anymore.
3) Item series- Basic as well as better quality series offered over the decades. Price depends upon exactly what you have
4) Competition with cheap imported ****. I prefer Starrett scales (rulers) over all other brands for several reasons, most of the garage shop types will buy cheap imported items because they don't know/need the difference. Same goes for mics, indicators, or about anything else bearing the name Starrett. The audience you sell to will make a big difference.
5) Items in wooden cases bring higher prices than items in carboard boxes or plastic. Missing accessories affect prices too.
I'm a retired toolmaker so I don't need any more tooling for the job, this is all just my opinion. Would help others if you posted photos and/or list what you have.