An item is only worth the amount someone is wiling to pay
There are so many factors to consider, when thinking about price.
Price depends on supply and demand. The less quantity and the higher the demand, the more the price will be.
Price can also be dictated by the location of the buyer and the seller, for example a Dutch exclusive pony will sell more for someone outside of the Netherlands.
The platform the item is sold on, eBay, gumtree, charity/thrift shop, online collectors store, Facebook, Instagram, private Facebook groups, online forums etc. The price is NOT consistent, the selling platform can have a big role in the price on an item. This makes price checking hard now a days, plus many things are sold behind closed doors.
Many Nirvana ponies have always been expensive, but the value on money also changes (think exchange rates). When there was the financial crisis back in 2008 or so, the price of many Nirvana drastically dropped, some of the Greek ponies, lost more than half their value. It was also a time when many people started to liquidate their collections, when again effected the value.
Another big a factor is TIME. I started collecting in 2003, G1 ponies are harder to find now then when I started collecting. Think about it, G2 and G3 ponies are now classed as vintage toys.
I think also we have new collectors and they will influence the market too.
Love pkw xxx