Donny was charged $1.5 x 6 = $<<1.5*6=9>>9 for the small apples.
He was charged $2 x 6 = $<<2*6=12>>12 for the medium apples.
And he was also charged $8 x 3 = $<<8*3=24>>24 for the big apples.
Therefore, Donny has to pay $9 + $12 + $24 = $<<9+12+24=45>>45 for all the apples.
#### 45