Look, I shouldn't have to explain how glamour is different from a leveling potion. It's obvious: one unlocks content, one doesn't. The slippery slope argument is an alarmist fallacy because the difference between the two isn't just magnitude (which is what slippery slope arguments rely), it's a difference in kind.
Furthermore, that's totally off topic anyway. The point is that the items are appropriately priced relative to the demand, the only way to get the price lowered is to reduce demand (ie, not buy it). Complaining online is much much less effective.