So 1k sat fee to send 1 million sats that’s not bad. It’s just the mining fee that’ll get you.
Page 6 here cofirms they cahrge a flat 0.1% fee. Anything more than that appears to be the onchain fee to sent to your wallet
https://sideswap.io/resource/pdf/SideSwap_-_Peg_Service_-_Briefing_Book.pdf
So 1k sat fee to send 1 million sats that’s not bad. It’s just the mining fee that’ll get you.
custodial lightning is often worse