Screw it, I've just bought four of the MSI Ventus 3X for £399 each.
No, they're not a bargain, but we have need for 16GB CUDA cards and as pathetic as these are, they're still the cheapest 16GB cards you can buy. I was ranting about how terrible they are compared to the A4000, but not everyone needs actual GPU performance, simply the ability to hold the entire dataset in VRAM on the GPU.
I'm treating them a bit like those shitty Geforce GT730 cards with 4GB of DDR3 having some non-gaming uses while Flagship cards from the same era like the 780Ti were limited to 3GB GDDR5. They'll run workloads that more expensive cards won't. They will not run them well, but any result at all is better than crashing out with an error.