When did the price of Unis skyrocket?

I've been collecting tamagotchis for a long time but sometimes I go into hobby fatigue and stop paying attention to what's going on. I already have an Angel Uni from when they were being sold retail and I decided that I should get a second Uni to customize and because I always like to have at least two of each color tama in my collection.

It wasn't very long ago that I saw the pink and purple Unis being sold retail for the standard price. But when I checked today only third party sellers had them for around $100 (USD). After that, I checked Mercari and eBay for something secondhand, but I couldn't even find an out of box one for under $150! Usually, it takes ages for a tama to be off the retail market for prices to climb anywhere near that high. When did this start? What the heck happened? haha