Also don't forget that Ark tx has to be in every single block if there was at least one tx between them. So yeah, if everyone uses it then it might scale well (infinite number of txs squashed into just one), but if only few people use it the ASP would pay enormous fees to keep it all running. See the current fees and estimate how many transacting people it needs to split the anchor tx fee between them, cover the cost and maybe earn some extra? And if we want this thing to be decentralized, we need multiple such ASPs, and each will be sending their transactions trying to get in every block or else the whole vUTXO trick becomes unreliable.

In LN you only pay twice per channel, no matter if it's used or not.

For some reason this little technical quirk isn't highlighted on their website arkpill.me. Maybe I misunderstand something, but this is what I got from the twitter discussions.