I’m an economist. This is an example of a volume discount. Prices often decrease per-unit when buying larger quantities. That happens whether it’s milk or the square-footage of an apartment. I’d expect larger files to be worth less per-byte. Photo and video files tend to be larger than text ones.
I would think classical mechanisms of price determination don't really make sense when there's a brand new market: customers don't know how much things "should" cost and businesses can't make decisions via comparison to competitors. So there is some arbitrariness in setting the initial prices - you can't do market research without an established market.
This is especially true with these data brokers, since it's not like "cost of materials and labor + a profit margin" makes sense. In this particular case data is more like a new commodity than a manufactured good.
Do you really think that market prices are going to reflect such a popular adage because a picture really is worth 1000 words? Does this kind of pricing differential get reflected in the salaries of journalists vs photographers? No? Then as someone else said it's a new market with an artificially "for lolz" initial price that competitors are blindly copying to avoid having to do their own price discovery. I'd expect this to shift & correct slowly over time unless it's a cute joke that everyone appreciates & the true price is close enough that no one cares enough to differentiate in that way.