That's f*cking sad that there's a SEALED SEALED Duo. Looks like my box. Great condition but not in a god damn case. What's funny is this guy thinks that this is ok and someone will pay $5k for it. Why is it that it's mainly the US Duo stuff that's so freaking outrageous? I'll just never get it. If all these people are willing to pay a premium for US stuff, where the f*ck were they when it was release and on the shelves?
They were in school or preschool.
Duo stuff is uncommon, but the number of overall titles is small, so it's very attractive to people who collect instead of play as a hobby to quickly cobble together another complete collection. It takes more money than effort to do quickly, which drives up the prices, which makes collecting Duo stuff all the more attractive to people who value items based on what other people think that they value them for.
and then the good guys like us miss out on a lot of great games cause the price is too high to afford getting them all 
As far as I know, games like Dynastic Hero and the System 3.0 card were never for sale in stores. I bought pretty much every game I wanted and all the hardware when they were new.
For all the people who say, "if only we could buy them at retail", aside from the cost in developing a time machine, 99% of all Turbo/Duo stuff is cheaper than ever.
TurboDuos were $550 here. With inflation, that's something like $850 now. Factoring in 16-year-old-in-high-school dollars, it would be the equivalent of no less than $100000 in my adult-with-a-full-time-job dollars. Games sold in Canada back in the day would be around $125 today. Add up what it would cost to buy them all new and subtract the highest prices all the games go for anywhere today. I paid between $100 - $230 for a lot of PCE and Saturn games when they were current. There was a time when I'd save up for weeks or months to buy a new game. I could buy practically any Turbo/PCE game if I saved up months worth of spare spending money today.
It sucks that original copies of anything we want aren't basically free, but the state of the Turbo/Duo collectible market is literally a dream come true for me. So much more so for PCE stuff. Especially when roms and isos are available for free. So many games were impossible to track down at the time and even for a decade after. And that was only for the tiny number of games we were even lucky enough to hear about. Now we know about everything and can try a game we just discovered within minutes.
There's never been a better time to be a Turbo/PCE fan.