I'm guessing history wasn't your best subject in school. The Millers have paid the LT twice when they had a team poised to make some noise in the playoffs.
As for them selling off picks, there are multiple reasons why they do that sometimes. The Jazz spend a lot of time researching players, and sometimes they just don't expect any players of interest to be available where they will be drafting. They also don't ever want to be carrying a whole bunch of rookies in any given year. 3 rookies in one year is usually the limit, and sometimes roster spot limitations prevent them form even carrying that many. They have also proven to be willing to buy a pick when there was a player available they wanted. That's how we got Rudy Gobert.
Anyway, there are lots of examples of the Millers spending to make the team better, when they wouldn't have if there was any truth to them running the team cheaply. One of those examples was choosing to match Hayward, when about 60%-70% of the fan base wanted them to pass. Matching that contract was a big gamble, as Hayward didn't have a great season leading up to it. Fans cry and complain now that the FO didn't just max him and get the extra year, and even though he has proven to be worth it, that contract was a big gamble that could have backfired.
The best example was their decision to build from the ground up instead of continuing to build a mediocre team to chase the 8th seed. That's a really hard choice for a lot of teams to make, as they lose quite a bit of money by missing the playoffs for multiple years.
The jazz have no doubt, made some mistakes over the years, but the salary cap makes it extremely important to spend money intelligently. Teams like the nets and Knicks have proven that not only does throwing money around NOT guarantee anything, it can cause you big problems that take years to pull out of.
Utah has been one of the better run organizations over the years, and just because the Millers don't throw money around like Brooklyn, doesn't make them cheap. It makes them smart. Calling them cheap is absolute nonsense.