ERC20 / DEX / Fee’s – Question

Hi

I have 3 different ERC20 tokens in my Wallet and i wanted to send them to an exchange but every transaction fee would be ~12$.

So i would have to pay 36$ fee for sending them to exchange.

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I thought maybe swaping them on a DEX (uniswap, kyber,. …) to ETH and then send the ETH to an exchange could safe me money.

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i loged into a Dex and wanted to swap ERC20 tokens into ETH but i always get the message " Your ETH balance is not enough to pay for the transaction fees "

but i have 150$ worth of ETH on that address. Does it mean to swap ERC20 tokens to ETH on a DEX does cost more 150$ ???

I can't believe that. what is wrong that i can't swap my tokens to Eth?