Why is there such drastic values for old cards?

I found all my old cards from when I was a kid. I have many rares and first editions from the original 1995 set. I’m trying to value them but there is HUGE price differences when looking up a card. For example, I have a 1st edition aerodactyl 1/62 holo. When I did a search, it’s listed for $15.99 on troll and toad, but then people have the same card listed on eBay for around 300 dollars. I am certain it’s the same exact card and mine this one is near mint. I have a lot of cards that are listed for around 20 bucks on troll and toad but also listed for several hundred on eBay...

So what’s the deal, are these people on eBay delusional?