The initial pricing put out by second.tech reflects the cost of on-chain operations at at very very early stage in Ark's development. The more Ark users there are, the cheaper the refresh fees will be, since they can be split between everybody in the Ark... happy to be corrected but I believe that this will be a linear proportional relationship. I don't quite understand what you mean by custodial swaps (possibly my lack of knowledge); I was under the impression that boarding and exiting the ark is completely non-custodial since the mechanism is multisig transaction-locks.