Bottom line: It's not.

Salt water chlorination systems (SWCG) are great, especially if you travel and can't watch your pool every day. But they can only save you money if you don't have to hire a pool service because you have one!
They simply will cost more than just use sensible maintenance methods. I took care of my first and second pools for 13 years without an SWCG and only installed one because we travel a lot more now. I love it but it does NOT save me money.

Second point: People are sold SWCGs by pool companies with they idea they don't have to do anything to have clear water. Very dangerous. You will be MUCH better off learning the simple A-B-C's of pool care we teach here and our recommended BBB system (for Bleach, Borax and Baking Soda). So you'll be FAR better off if you read up here and on our sister site PoolSolutions.com on how to use these methods.

They are easy. You do need a good test kit (we recommend the Taylor Technologies K-2006 and K-2006C kits). The methods are not magic, the chemicals are not mysterious or magical. But you do need to master them and comprehend them. Once you do, THEN if you add an SWCG to your pool, you'll know EXACTLY what to expect and how to enjoy it.

But, since you are getting the pool with an SWCG, it doesn't mean you NOW have to depend on it. I still recommend you learn how to take care of your pool without it, which isn't hard, and THEN let it make your job even easier.

However, to be frank, I have NO idea what the 16 Week Chemical Packages are, though, obviously, one is supposed to be good for the season. And $399 for chemicals for the season is far MORE than I would spend on my pool each year BEFORE I installed the SWCG. If I spent $200/season it was a lot.