Thing is, no payment besides fealty is going to be enough. Not sure how much you know about the background, but we are planning to invade Westeros pretty soon. We are not foolish enough to grant additional power to a fey Court in a land we plan to conquer without their ironclad allegiance.
I'm aware. I meant in terms of the oath being the payment, as, after all, we seem to be willing to have the oath go a number of ways.
We obviously want them to swear to us, but I'm pretty sure I recall us stating that we are fine with her swearing to another lord, even one that isn't yet working for us, as long as the lord isn't a total fool, so that's also on the table. There's been no mention of it but I'm pretty sure we'd agree to give up the crown in exchange from the Reach/Tyrell swearing loyalty to us, which, I mean, they do want the crown as well.
Sure, the Reach/Tyrell's probably aren't willing to become our vassals solely for the Crown ... but it's also not like the Crown is the only reasoning for them to decide to become our vassals. There's a ton of other reasons for them to support us in the coming war, even the simple fact that we are real powerful, so the Crown might simply serve to act as one coin among many to buy their services.
So the fealty is, probably, the only acceptable payment (I say probably because, well, you never know what they might offer. Even just something like some really detailed oaths that set established rules/behaviors that would stop them from being a problem while not actually working for anyone foreign might do it, as long as it's backed up by other stuff). The only question is, well, who the payment is coming from and who it's going to.
Edit: Actually, the agreement thing might be acceptable? Like, clearly fealty to us is best, but Fae can't exactly lie or break their agreements. If they swear a detailed enough oath that assure us that they will be beneficial to the realm and not really act against it or anything, an alliance instead of part of the kingdom ... it might be possible? It would have to be real detailed, with no loopholes, nothing overlooked, and with part of the oath on not interfering too much .... but it might be workable?
Clearly, fealty to us is best, but we should seriously consider what kind of terms would we be willing to go for if fealty is impossible. Cause I get the feeling that just never trading it to them would make an enemy of the Fae and possibly the Reach as well, so we should seriously think about if there are any terms we'd be satisfied with aside from straight up swearing to become our loyal subjects.