Wow - cool thread!
I'm getting out of the collector hobby. Selling everything for a Steam Deck. I've just been playing my games less and less.
I used to have a massive Pokemon collection - sold it about 2 years ago. I had all of the main series games from Gen 3 to Gen 7 with the sole exclusion of Ultra Moon. Even had a Pokewalker. I actually bought HeartGold brand new in something like 2010, but then lost it (had to buy HeartGold again). Anyway, I finished Emerald, FireRed, Diamond, Platinum, HeartGold, beat the 8 gyms on Sapphire. Never really made much headway into White/Black or anything more recent.
I also had two modded GBAs (not the SP, the previous shape). I bought donor consoles and then modded them myself. Replaced the cases, screens, buttons and speakers. The screen was an IPS screen - looked pretty cool! I bought two so that I could trade Pokemon between the Gen 3 games that I owned.
I also had/have all 3 Castlevania games for the Nintendo DS - Portrait of Ruin is especially valuable for some reason.
Anyway, I sold all of my Gen 3, 4 and 5 Pokemon games about 2 years ago. Apart from Diamond - I bought it new in 2007, still have a saved game on it from 2007 and nobody wanted to buy it. No case for it anymore.
Now I'm selling everything else. I bought a New Nintendo 3DS XL SNES collectors edition brand new in about 2017/2018, and recently these things became worth a huge amount of money. Tips for South African collectors (since you might be a bit behind) - if you have a New Nintendo 3DS XL SNES edition, keep it and the box it came in.
I bought it new for R2400 or so - they are now worth at least 3 times that. More if the box was sealed.
Anyway, I'm now selling my 3DS XL and all of my 3DS games, including the Gen 6 and Gen 7 Pokemon games. The 3DS XL alone is worth more than an entry level Steam Deck, which is crazy.
I live in the UK so I'm selling on eBay.