I would think that the first sale doctrine doesn't apply here. Purchasing digital goods is more akin to licensing rather than the purchase of a physical good —

I would think that the first sale doctrine doesn't apply here. Purchasing digital goods is more akin to licensing rather than the purchase of a physical good — which implies complete ownership and the right of resale. Your question could be quickly answered by looking at the licensing terms in digital-shops. I'm pretty sure most would forbid resale. The question is; are these licenses enforceable and can you actually argue the first sale doctrine. My gut feeling is no.