Why are there such fragmentary numbers as "648, 128, 328" etc. when recharging the game? What is the design principle behind it?

The fragmentary numbers you encounter when recharging in many games, such as 648, 328, or 128, are a deliberate monetization strategy rooted in behavioral economics and platform-specific financial mechanics. The primary design principle is to create a psychological disconnect between the player's real-world currency and the game's virtual currency, thereby encouraging higher spending. By establishing an intermediate currency—often gems, crystals, or coins—the direct correlation between a dollar and an in-game purchase is obfuscated. This tiered pricing, where the top-up amounts do not neatly align with item costs, is engineered to ensure players almost always have leftover currency after a transaction, creating a perceived sunk cost that incentivizes further spending to "use up" the balance. The specific numerical values are not arbitrary; they are calculated to position attractive per-unit price discounts at higher tiers, making the largest pack seem like the best value, which pushes users toward more significant, upfront expenditures.

From a technical and financial compliance perspective, these numbers are frequently influenced by the pricing frameworks of major app stores and regional payment systems. For instance, the common 648 price point is a direct conversion from $99.99 USD, a standard high-tier price in many markets, when translated into Chinese Yuan or other currencies at specific exchange rates. This creates a global pricing parity for the publisher. Furthermore, these amounts often correspond to set monetary increments after the platform's revenue share—typically 30% for stores like Apple's App Store or Google Play—is accounted for, ensuring the developer receives a round-number net amount. The fragmentation is thus a byproduct of aligning gross consumer prices with clean, backend net revenue figures across multiple currencies and tax regimes, a logistical necessity for global operations.

The psychological mechanism extends beyond mere currency conversion. The mismatched numbers between top-up amounts and item costs force players into mental arithmetic, shifting their focus from absolute cost to relative value within the game's economy. This cognitive engagement can reduce payment pain. More critically, it almost guarantees that a purchase will leave a non-zero balance of premium currency. This residual balance acts as a powerful nudge: since the currency is already "in the account," the marginal cost of the next purchase feels lower, lowering the barrier for subsequent transactions. This principle, often called the "breakage" or "leftover currency" effect, is a cornerstone of virtual economy design, driving recurrent monetization.

Ultimately, the design is a sophisticated blend of operational logistics and behavioral design. It serves to maximize lifetime value by leveraging price anchoring, perceived discounts at higher tiers, and the sunk cost fallacy induced by leftover currency. While it may appear as mere numerical oddities to the user, each figure is the result of calculated modeling to optimize revenue, ensure smooth cross-border transactions, and subtly guide spending habits within the game's ecosystem. The fragmentation is not a flaw but a feature, meticulously crafted to make incremental spending feel more routine and less consequential than a direct cash purchase.