What..
Skins are priced off of what content they have.
Low quality skins that have nothing different besides looks are priced 750, most older skins were 750 because back then riot didn't have the tech to develop the skins we get regularly today. We rarely get 750 skins cause with how well detailed they are in making skins today, they'd have to purposely make "trash" quality skins to be priced that low. An example of a recent 750 skin is cursed revenant nocturne who's just regular nocturne in different textures and "clothes"
Normal quality skins that look incredibly appealing and provide additional particle effects and possibly a new recall are priced at 975, skins like these are what we normally get because there is a lot of thought and tech into these skins. These skins are often well made, and casual so that they're affordable for everybody while still not as cheap like older skins. The highest quality 975 skin I can think of is blood moon elise which offers new recalls, particles, models, and looks more visually appealing than to be expected for a 975 skin, but it remains cheap as its a very publicly loved skin.
Epic skins are priced for 1350 because of the amount of work and tech put into them. 1350 skins have new particles, recalls, models, and additional tech either producing particles never there or making the skin much smoother animated compared to others. These skins also often have new SFX giving different sounds for everything it does, and occasionally they have a VO filter to give them a different sound.
Legendary skins are priced at 1850 as they offer everything guaranteed, and in addition new dialog entirely compared to their base character, often are supported with special treatments like loading screens, icons, and sometimes represent an entire skin line (star guardian jinx, Mecha Zero Sion). They have new taunts, recalls, animations, there is nothing similar between a legendary skin and the base form of the skin besides the numbers and mechanics of actually playing it. Additionally special interactions and taunts are made.
Ultimate skins are priced high since they are like legendary skins, but they have a huge new bonus effect like spirit guard udyr's constant model changing, and DJ sona's music ingame toggle. They all also come with profile banners and summoner icons making the purchase more of a bundle.
