You can get to the PH for 60 Baht ( USD 1.75) by using the Airport City Link and then transferring to BTS. When it first started it wasn't too bad but the service has declined, both in respect of frequency and the quality of the experience.
I used to take it in bad weather situations , on hand carry only trips. Now it has become very crowded and uncomfortable and no longer a viable option for me.
I use a car service : AOT is now around 1100 to lower Sukhumvit . I prefer to use SP Limousine @ 950 ( Camry or Teeana). Extremely reliable, very good drivers. I've used them at least 30 or 40 times in and out. Using a taxi is just not worth the hassle ( rogue and lunatic drivers, underpowered aircon, limited luggage space, possibility of "hot" meter).