Factor 1: Slippage
If the user is trading on DEX of the AMM mechanism, slippage will occur during the transaction. The slippage mainly depends on the LP (Liquidity Providers) depth and the amount of the transaction. When the liquidity is relatively low, the slippage is larger, resulting in the user will receive tokens less than expected.
Factor 2: Burning mechanism:
Transfer and burning mechanisms will be set in some token economic models. For example, 10% fee will be required for each transfer, of which 5% will be proportionally distributed to token holders, and the other 5% will be divided equally and injected into DEX to provide liquality. Therefore, uers may receive at most 90% tokens.
Factor 3: Dark Forest:
The mechanism of the dark forest is a privileged use for the Mempool packaging, which takes advantage of the feature that miners will preferentially pack transactions with high gas prices.
Taking Uniswap as an example, there are trading robots to monitor Mempool transactions on the Ethereum network. If there is a large-value transaction, the robot will immediately issue 2 transactions, one of which allows miners to pack first through a higher gas price, so that the token can be bought in by the robot before the user, and the other is also can be sold out by the robot after the user. After lower buying and higher selling, the trading robot will make a profit. At this time, the user will receive less tokens than expected.
There are common DEXs on the market, such as Uniswap, PancakeSwap, MDEX, JustSwap, SushiSwap, etc.