it really depends - White Rotaries came in a lot of variations, some worth more, some less.
A lot would depend on the case/cabinet.
A more plain White Rotary, no attachments and NOT in a really nice case/cabinet for $40, I would have passed.
No bobbin is not a big deal, but if it had no bobbin carrier, that IS a big deal. They aren't that hard to get, but it will increase the cost. For some machines, if the carrier is not there, you might as well pass as you'll never get one unless you find another machine with one. But I will say - if you are a collector, sometimes the best example comes cheap without a carrier, and they you find a junky version with the carrier.