The MTX effects are overpriced because they want people to gamble through the loot boxes, and end up spending more than desired.

For example, they would price the shop-purchased MTX effects at ~£20, and the loot boxes at ~£2. People end up buying several of them because they feel as though £20 is overpriced, and the illusion is that they might get something of £20 value through the £2 lootboxes. Realistically though, those £20 cosmetics would be priced at like £5 from any other game that offers something similar. People would never buy the shop-sold MTXs straight up but ultimately they end up spending much more than just £5 (or evn more than £20 before they call it quits) on average due to lootboxes. Lootboxes are the illusion of value. An individual is more likely to spend £20 in £2 transactions as opposed to straight up £20. This is the mentality that lootboxes (and GGG) prey upon.