My brother went to school with Bill Weaver Jr; him and his father had a monster truck in the late 80s called Rambo. Bill Sr was on the original board of directors for the MTRA. Back in 1989 his truck alone was over 100 grand as it sat. That doesn't include the support trailer, tow rig, mechanics, licensing, spare parts etc.
By the time I was around, his truck was appearing regionally when the events came this way; but it was mostly used as a promotional tool. They built another truck 'Rambo Jr' which was a street legal lifted truck; his wife used to drive it to the store LOL.
I spoke to Billy about 10yrs ago and they were trying to get funding to update the truck, but I don't think it ever happened. People really want that 'freestyle' stuff with backflips and blowing through campers...they can't afford to do that.
Monster truck photo album