£150 for 3x500 stickers at Amazon. That should leave you missing approximately 75 stickers, which you can buy as singletons directly from Panini, at £0.25 a piece. So you can do it for £170 with absolutely no social interaction required. Definitely an unreasonable amount for a bunch of stickers, but still peanuts compared to what a freemium video game can cost.

Just to be clear, sticker collection economy is also shady, it just doesn't have a societal impact remotely like that of loot boxes.