A good time to sell them would be now since it looks like someone bought out the ones that were on market, so the lowest is 27k.
It'll probably soon go down to about 18k again which has been the overall average price of shutter shades over the past few months that they've existed.
So yea, if you're looking for a profit, I wouldn't invest in buying those glasses right now, but rather wait till they go down around 15k or so, so you can get them at 10-13k-ish, and wait for a time like this where you can sell them for 20k+.
So yea, the price is very unsteady, but at the moment they're worth 18-24k