I am getting prepared to add a seperate fill/drain system from factory MLS system to my 2011 VLX. I am adding the 750 lb bags to each compartment. The price for $200 is pretty reasonable. I am looking at approx. $300 per side with the JABSCO pumps, 1" thru hull intakes, ball valves, 1"line, hose clamps, quick disconnects, etc.... this does not even include the 750lb bag which would have added another $300 to the total cost.
I have shopped around online and wakemakers seems to have the best prices on bags, fittings, and pumps. They are also very knowledgeable on ballast systems and have very good customer service if you ever have any questions.
The cheapest option for you would be to spend $100 for a portable Tsunami pump to fill and drain the bags.