Its hard to say what cost would be but I would try to pick up stuff used on the forums and save that way. I bet I could do the whole thing for around $1500.
Mangroves have done well for me if the water parameters, mainly Magnesium so I understand, are kept up and the leaves are sprayed down regularly to remove salt deposits. When they don't do well they drop their leaves then die. Just wondering, what do you pay for Mangroves online?