I wrote the following formula which works but it is a mile long and
some of the functions are used more than once. Intuition tells me that
there should be a way to shorten it (i.e. make it more efficient).
I've been trying to do that for hours but my logic simply fails...

Anyone wants to give it a try?

=IF($BC15="PD",IF(OR($R15="INT",$R15="NEE",$R15="O BS"),$J15,IF(AND($E15=
"IT1L",OR($H15="RA",LEFT($D15,3)="1K0",LEFT($A15,3 )="60W",LEFT($A15,3)="
70-")),IF(AND($AS15=$BG$2,$AV15=$BG$3),IF($K15$J15 ,$K15,CEILING($AV15
*$BG$4,$J15)),MAX($J15,$K15)),MAX($J15,$K15))),IF( $BC15="X1",IF(AND($F15
="F",$G15="V"),IF($AV15*$BG$5MAX($J15,$K15),IF(H1 5<"RA",CEILING($AV15*
$BG$5,$J15),IF(CEILING($AV15*$BG$5,$J15)<500,CEILI NG($AV15*$BG$5,$J15),I
F(CEILING($AV15*$BG$5,$J15)<=5000,IF(MOD(100,$J15) =0,CEILING($AV15*$BG$5
,MAX(100,$J15)),CEILING($AV15*$BG$5,LCM(100,$J15)) ),IF(CEILING($AV15*$BG
$5,$J15)<50000,IF(MOD(1000,$J15)=0,CEILING($AV15*$ BG$5,MAX(1000,$J15)),C
EILING($AV15*$BG$5,LCM(1000,$J15))),CEILING($AV15* $BG$5,MAX(2000,$J15)))
))),MAX($J15,$K15)),IF(CEILING($AV15,$J15)<=1000,M ROUND(CEILING($AV15,$J
15),$J15),MROUND(ROUNDUP($AV15,-2),$J15))),"problem!"))

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tb