Not what it should be, that's for sure. ROI is much better with SEO. Why rent traffic when you can own it?
SEO requires a lot of time and commitment or $$$ if your paying someone to do this properly. Long term I agree that SEO provides a greater ROI however, it is not as simple as SEO v CPC you need to look at the product, company and market and decide which model fits best. e.g. a seasonal fashion product would find CPC provides a greater ROI than SEO
ROI is normally done in percentages So 100% ROI on $1 would be if you spent $1 and got $2 back (initial $1 plus $1 profit)