Keltham is now feeling wobbly for a different reason, which is that he'd thought Yaisa's price was inclusive of that sort of thing... well, hence having a first week to work out things like that, he guesses? He is not very willing to go above his present price, before his wages go up, possibly even after they do -
He's just going to think about this later. There are proverbs about this kind of jarring clash of financial expectations even when people aren't aliens, and it's important not to let them run over your feelings too much. This probably wouldn't even feel so jarring if he hadn't otherwise mentally overworked himself the previous day. Possibly Yaisa literally was just trying to make him feel more comfortable. Carissa sure was.
"Thank you both Yaisa and Carissa," he says, instead of anything more complicated than that.