depending on the project there sometimes is not any monetary savings. the advantage of DIY is the fact that the finished project will be exactly what you need. aquariums, regardless of whether it is FW or SW are individual entities. no two are exactly the same. either finding the correct coloured stand to match the decor of the house or finding a sump that can fit behind a stairwell. sometimes the product you need does not exist. luckily aquariums are very easy to modify, or finding other products to modify for the situation is pretty easy with enough research.
G~