I have a two-week trip to the US coming up mid-February on an open-jaw ticket arriving in SEA and leaving from DEN, and now need a flight between the two. I can use KrisFlyer miles to book on UA or Qantas FF points on AS, but only economy awards are available for the flights/timings I would be interested in. I was therefore thinking of booking a cash fare in First instead on AS 710, for which the prices are currently $71 (+ $30), $104 (+ $30) and $244 for Saver, Main and First respectively.

I was wondering, given these prices (+ $30 is for checked luggage), whether a cash fare in First would be worthwhile, or I should just go Saver/Main instead, perhaps using miles. What tempts me in part is the possibility of checking out the AS lounges at SEA, since I shall be travelling on the penultimate day when access will still be granted to those travelling in First on a shorter flight. I know this is only a question I can answer, but any thoughts and perspectives would nonetheless be appreciated.