i think a lot of it has to do with COVID. I know that seems like a convenient excuse, but hear me out. For one, people are obviously spending more time at home, which leaves them to find ways of entertaining themselves outside watching TV and eating. I'm sure a lot of people who'd otherwise have written off the idea of buying an SNES and some games on ebay, are now wanting to seriously do it since they don't have anything better to do while being stuck at home. However, there is another big piece of this puzzle as well. The stimulus checks.
I'm in the process of building a new gaming rig and the reason why it wasn't finished weeks ago is because of the massive shortage in PC parts. Some of this is due to supply chain issues, but a lot of it is also tons of people rushing to various computer stores and buying new high end graphics cars, RAM, and Motherboards with the $1200 that appeared overnight in their bank accounts. I think for a lot of people who are heavily into collecting right now, that money is instead going towards games they maybe haven't purchased due to it being too expensive or not having the money to buy them. I know that if I was in the collector mentality I was in 3 or 4 years ago right now all $1200 of my check would have gone towards several high end, rare titles to add to my collection. I'm almost certain this is responsible to a decent degree in the spikes in value.
As to whether or not these prices are sustainable, I think the short answer is no. Obviously everyone's $1200 will be gone soon as will the stay at home orders, business closures, and other forces requiring people to stay at home. As a result, your non-collector 30-year old coworker who bought a Genesis and half a dozen games off ebay will likely sell it once he's able to go back to the gym and go out drinking with his friends again. This will cause a large influx of retro games and consoles, bring the prices back down. I think if the economy ends up going into a death spiral like many economists are predicting despite what the Fed is doing, then you could see a radical decline in prices as video game collecting will take a major backseat to people just trying to survive.