Re: It was worth every penny...
The original (plug-into-the-TV) Vega console was successful, so it wasn't unreasonable to assume that this one wouldn't be.
There's also the fact that the Vega+ (like the Vega) was only ever meant to be an emulator rather than a hardware-level recreation anyway, so it was already a solved problem; there must be countless low-powered systems that can run Linux or Android and an emulator on top of that. If- as I'm guessing- there are companies in China use these as the basis of pre-existing cheap, generic handheld designs, then that's practically an off-the-shelf solution.
It's not like the Vega+ looks much like the original Spectrum (unlike the original Vega's bizarre parody of the original Spectrum design or the proposed Spectrum Next's "Plus"-inspired design). Stick a rainbow flash and "Sinclair" logo on an existing design and it would have worked within the £500,000 budget.
In short, there's no reason the Vega+ shouldn't have succeeded. Its problems had nothing to do with hardware and everything to do with business politics, power-grabbing, infighting and incompetence.