In my searches the Droid factory R2 is easy to find, but in crummy condition. Minty or even nicer version are rare and go for good money. Jedi Luke is easy, even in good shape, but the snap cape and blue saber may be the cost factor for you. Bought an original Luke Jedi blue saber for $30 last week at a toy show. I didn't need the snap cape, but they were selling it for $30 as well.
Also with the snap cape/ blue saber Luke you've got to make sure you have the correct COO stamp. Neither are super rare, just in shorter supply than mainstream figures. R2 is just tough to find with a nice sticker, sort of like a nice red bar R5.