Best thing to do is state origin in the first post as then we can give better advice(If a season or pass is already held for part of the journey, let us know that too)
The above advice assumes you want a single (e.g. if you are flying and won't be returning within 1 month or will get a lift back) as you suggest you only want to travel one way?
However if you do actually want to return, then I would not bother with Advance fares, and would get an Off Peak Day Return (£15.85) if returning same day, or an Off Peak Return (£18.30) if returning within one month.
For a single, a single from Ravensthorpe to Dewsbury/Huddersfield, followed by an Advance from there to Manchester Airport would be much cheaper than a walk-on ticket.
The reason for this ticket being so expensive is because of the tunnel between the Pennines!
Ravensthorpe to Mirfield is only £2.05, and Greenfield to Manchester Airport is only £3.40 (includes the tram from Man Vic to Man Pic), however just to the one stop between Mirfield and Greenfield costs a whopping £8.95, as this fare is not subsidised by either PTE.
The cheapest split would perhaps be Ravensthorpe to Stalybridge (£9.30) and Stalybridge to Manchester Airport (£3.40), the tram is included if you go via Man Vic. This would be valid on TPE trains that call at Stalybridge, or Northern stoppers, but you can't pass through Stalybridge non-stop (unless you ask the guard and he/she says yes)
