Having had both a planted tank and a saltwater reef (years ago), this is my opinion:
Planted tanks are a lot cheaper, but a lot more difficult. The learnng curve is a lot steeper than with a reef tank. It is a lot easier to remove all Nitrogen and Phosphorous and dissolved organc compounds with resins and protein skimmers and in some cases denitrification filters and these days biopellets.
It is harder to maintain a balance of nutrients, carbon dioxide and light in a planted tank. Also on the subject of how much advanced equipment there is for saltwater compared to freshwater... Think about it. Planted tanks don't need the intense light, the protein skimming, the complicated sumps, reactors, resins.
In addition to this, the biodiversity in a saltwater/reef tank is extraordinary! There are so many types of shrimp, coral, fish, snails, crabs, starfish etc. The colors and patterns of most of the commonly kept fish are incredible and the corals turn fluorescent under actinic light, have interesting behavior of their own (eating, moving.)
I think that saltwater creatures are very "alien" and novel and that is what draws some people do them, while freshwater is familiar and boring to some. I think saltwater offers a gaudy sort of beauty with an immediate bang, while freshwater offers a more subtle beauty that takes a special type of person to appreciate.
One thing I would like to mention is that I hate it when people cut corners and are cheap. If you want thw hobby to advance, then you should support the companies that do research and development of aquatic plant/ fish products. DIYing (with some exceptions, like filter floss, etc.) does not help advance the hobby. Am I saying to go out and buy an ADA Grand Solar for your tank? No, but I am saying that if you want to advance the hobby, don't buy a Hamilton Bay desk light from home depot just because itis "good enough." Using DIY yeast in a milk jug does not advance the hobby.
I am not putting people down who can't afford the nice aquarium equipment and DIY out of neccesity, but I think beiing cheap for the sake of being cheap does the hobby a disservice.
Saltwater setups are only as expensve as you make em and there are different levels of difficulty and expense, just like with freshwater. You can easy coral like mushrooms and various soft corals that can live in relatively low lght, with a bit more money moderate difficulty you can have LPS which are my favorite, but if you want giant clams, SPS coral and anemones then that is a serious investment and commitment to the care and maintenance of these creatures. Dosing and light are critical as well as nutrient export. A $50-$100 plus coral that is slow growing is a lo different than a fast growing plant that costs $1-10 bucks. You aren't going to shell out a lot of money on livestock and then be cheap when it comes tp equipment to care for them. It is a recipe for disaster if you want high end coral but are cheap and lazy when it comes to light, maintenance, water chemistry etc.
You can grow coral under expensive LED's and expwnsive protiein skimmers and all the otherbells and whistles... Or you can have a basic setup with basic livestock under basic lighting and still be successful. It all depens on your budget, desires and commitment.