Well, the abs was $0.50 per foot. I used 9-1/2" so that is $0.30 per tube. The coupler was $0.79 and the endcap was 1.29 * 2 for a grand total of

$2.38

if I made 6 of them that will be

$14.28


Just the cups come to 2.22 so 6 more of those is
$13.32

Grand total with 2 cups like the ones that are sold commercially =
$27.60

differnce =
119-27.60 = 91.40

I can buy a hell of a wter basin for the waterbath for $91.40.

Now sure where you are coming up with the final price being about the same...