I have withdrawn and trade ETH from MEXC multiple times already and I am never charged more than $3 but when I swap ETH ERC 20 on Uniswap the gas fee is almost always $10 and few times over $10, why is it like this? Are DEXs suppose to be more costly normal centralized exchanges?
You have to consider tax rate from a token project. It is an extra fee and it comes from a project with their own policy to charge their users for any token transactions. Uniswap is only a DEX and they have their own swap fee policy.
When you swap a token on a DEX, there are two fees: DEX swap fee, token's tax fee that depends on each project team.