Yes liquid ferts are expensive especially growth products imo they are better left for the golf course guys. They do have a product I really like though
6-0-0 Xtra Iron gives me a good greenup on my St. Augustine and Centipede yards that dont need as much fert as the Bermudas also its a little cheaper than Nitro. If you really want to do some liquid ferts just get some Urea or Uflexx and melt it down in your tank you can get creative and add some Iron and Potassium maybe even a herbicide if need be. I do this quite a bit especially on new yards that need a big turn around quick.