I'm speaking off the top of my head, without the benefit of looking at papers and records, so I hope I'm basically right.
When Gary and George first presented The Star Wars budget to Fox, it was a very low figure, like $7.8M. The Fox accounting people looked at the breakdown and found it unrealistic. Fox accounting raised the budget to something like $9.8M. That was very early on. Then George and Gary went into preproduction, and left for the UK. I did a presentation for Fox's Board of Directors and part of the presentation was to ask for more money. This was the legendary Board of Directors meeting where someone asked if STAR WARS was a battle between Hollywood actors. Regardless of the confusion, the budget went up. Laddie effectively presented that the cost of ILM effects wasn't really known because nothing like this had been done before. The end budget was over $11M. The evolution of STAR WARS' budget would have been a subject which Jim Nelson could have expertly answered if he was still alive. RIP, Jim