An Ethereum transaction from one address to another costs $ 10.
The token transaction costs $ 40.
You could send Ethereum to the kucoin exchange and pay $ 10 in commission, and then buy DAI.
Instead, you do a swap ($ 40), a trial transaction of a small amount ($ 40), the main transaction($ 40). What for???
It is the point.
DAI is on ERC-20 chain and fees for DAI or any ERC-20 tokens are more expensive than Ethereum itself. With ERC-20 tokens, the smart contracts are more complex than Ethereum and their transaction fees are higher than ETH transactions.
Swap on any exchange or marketplace is always more expensive than you buy directly on the market orders.
You gave a very valuable suggestion for OP to avoid unnecessary costs from swap or token transactions.