134a question

I was recently shopping for a 12 oz can of 134a and noticed that some places it is as low as $8, and others it is $22 a can.
Is there a difference between the cheap and expensive 134a freon? if so what do I look for?
David
Lots of times the more expensive will have additives like sealants and lubricants or dyes you may or may not want or need. Other than, read the label carefully to make sure it's not some kind of generic replacement refrigerant. Make sure it's the real thing.