I don't think any UFAs would equate to a first round pick for just a few days of negotiation rights. Not that RNH would sign with Buffalo.
I hear you, this counter proposal to the OP has a few assumptions, like RNH signing with Buffalo. Obviously the Oilers wouldn't move heaven and earth for Eichel as he'd play behind McDavid and likely wouldn't move Draisaitl off of whatever line Tippett had him. The Sabres are reported to be asking for four first round assets. With the cap being what it is this was the best I could come up with.
In truth the Oilers need a 3C, a 2nd Line LHD and a top six LW. They don't need a star like Eichel, especially at the required cost.
I hope Buffalo gets a good return for him when he does get dealt. The fans deserve it.