LTVAs are $180. for the winter season. There are 7 or 8 of them scattered throughout southern CA and western AZ that you can move around to as you choose.
However, not all LTVAs have running water and dump stations. Most of them are simply cordoned off areas of BLM land with dispersed camping on other BLM land close by.
There are some rules that you should be aware of if you're not in a fully equipped (black/gray tanks) RV. Some of the LTVAs won't allow you to camp there at all without the tanks, some will allow you to camp but only within 500' of the vault toilet.
I buy my water at any one of the numerous water places in Blythe, Ehrenberg or Quartzite depending on where I am. Usually 5 gallons for a dollar.
There are dump stations in both Ehrenberg and Quartzite. Blythe has dump stations at a couple of the RV resorts. I'm not sure of this years pricing because I'm not there yet nor do I use them.
The laundromat in Ehrenberg has both potable water and a dump station - water is free if you're using the dump station. It's city water so I go up the road to the Glacier fill station anyways.
Weigh the cost of dump stations/water purchases against the LTVA fee and read up on which LTVAs have what facilities.
Personally, I like not being confined to camping within boundaries - for example, the LTVA at Holtville CA has no facilities so I couldn't camp there anyways. Right behind it is BLM land that is free and I can camp there. It means an extra 1/2 mile of driving to get to the hot springs every day...no brainer where I stay...