> Whether or not there are enough people capable of being in the translation market, there aren't enough actually in it to satisfy demand.
This is a largely semantic argument about how we describe the phenomenon of more supply coming on-line in a market when demand increases.
Does that definitional question really matter here? It has very little to do with the point that OP is making, which is that the pending translation needs of streaming services will easily be met if they pay more for translation services.
> There must be a structural issue on the other end causing the translations not to be valuable enough to the would-be purchaser to raise pay and clear the market.
One likely explanation is that for the people who actually pay for translation services, it is more profitable to queue up translation work rather than pay extra to accelerate it.
In other words, the issue is not that there is demand that is not being met, but is instead that demand for translation output (i.e. consumer demand for international streaming content) is not translating to demand for translation services.
Most likely, the amount of money that Netflix, etc, is losing in the short term not translating content is less than they would have to spend to accelerate the translation work.