I don't really like any of the fake stuff most of it just looks to fake and the stuff that doesn't is just as expensive as real rock
I'm not talking about sponge Bob stuff...LOL.
For my potbelly seahorses tank, I purchased wall hangings (I needed it big for the 90g) of a ships wheel and anchor, I then coated it with plastic resin to seal it, and attached it to dried out live rock with black pond foam.
In my 56g tank I used a tank decor column, but in the back, I used cake columns silicone to plastic shelves to be able to pile rock on top...in the other corner I used live branch rock (I needed it tall for the column tank)
The point is...you don't have to have just rocks, there is no limit to what you can use and do to your tank to make it look good to you. it isn't a cheaper method, just a different one. I like macroalgae so I have a ton of it in my tanks. The seahorses love it... and because they are such messy eaters, the macros help keep the water quality up.