Such a vast difference in prices and similar looking items
What you're showing looks like Scott #1299, a coil issue from 1968. Not really worth anything, though the variants (check a Scott catalog from the library for descriptions) might have some value.
A few things to consider:
1) make sure you're looking at "sold" listings, not active ones. You're as likely to find a seller who knows what they have (selling this stamp for $1 for example, as you are na´ve sellers or swindlers who lists it as "rare! yours for only $25!"
2) there are shenanigans to be found on eBay
, but I'll let others go down that rabbit hole.
3) sometimes, sellers honestly (or not) misidentify a variety, causing vast swings in price.
4) like most hobbies, the devil (and value) is in the details. Just as some pennies are worth tens of thousands because of a missing mint mark, stamp value is in no small part based on things like condition, perforation, grill type, ink color, paper type, etc.
If you can post 2-3 screenshots, I'm sure the community could dissect for you why the prices are all so different from each other.