Assuming an average training time of 1 week as you said, that gives us about 280k$.
It's also most likely trained for longer than a week, the base model for Dalle-2 was trained for 100-200k GPU hours, so between 2-4x longer than that, we can guess this is roughly similar.
You also never successfully train everything first try, so all in all, to replicate this work just from the paper, we are talking about at least 500k$.
I'll have to read the paper for more details, but it would almost certainly cost less (and take longer) to train a model like this in a more resource constrained situation than Google faces .
The shares would simply be votes towards future training dataset endeavors as no profit would be booked here. Say you buy 5000 out of 500,000 shares, that would give you 1% voting power in what dataset to train.
> 5 on-demand Cloud TPU v3 devices, 5 on-demand Cloud TPU v2 devices, and 100 preemptible Cloud TPU v2 devices for free for 30 days
So up to 7k hours on demand and 70k pre-emptible