What new standing sets?
The only new set would've been Seven's office which was pretty standard except for his computer which mostly was the reuse of M-5.
As well as mission control and the armature thingy.
Also, didn't Desilu (upon sale to Gulf+Western) change their billing practices wherein they went from getting somethings gratis to then having to pay for everything?
And that, I believe, was on top of overall budget reductions.