You can get Panasonic discs direct from Panasonic.com for cheaper, and free shipping after signing up for their 'club'. I bought a 15 pack in slim jewel cases for $20 shipped from their site, and they also have 25 pack spindles for $30. 3 packs of 5x were around $8 last time I checked, and you could get unrated (2x) discs for $1 each as well.
Regarding your question on why people use RW rather than RAM at times, one reason is that very few standalone DVD Players support RAM, while RW will work in most players. For data I do find RAM to generally be a better format though, but that depends on your needs - for example if you need the data discs to work on almost any DVD-ROM or DVD Burner, RW will have that compatibility while RAM discs will require a drive that supports RAM. And RAM uses write verfication during burning, meaning that a 3x disc actually writes at about 1.4x speed, meaning a full disc takes about 45 minutes to burn. A 5x disc takes about 24-25 minutes for a full disc. ImgBurn now supports burning DVD-RAM with verification off though if you'd like to try your luck there.