Multiple custom fields not calculating

We have a several workshops that require a Materials Fee aside from the actual cost of the workshop. So we set of the materials fees in the Custom Fields.

Workshop 1 - $7 materials fee
Workshop 2 - $15 materials fee
Workshop 3 - $15 materials fee
total should be $37 in fees it only displays the $7 fee and only one of the $15 = $67, omitting the other $15 fee

I went in and changed one of the fees to $20 and sure enough the all fees came through. $7, $15, $20



Is there a way to get this to work where both fees with the same amount will show up even if on separate workshops


--and then the question would go with if a couple both sign up, (so the quantity of the class is 2)-how can we get two materials fees to show up.

And adding to the weird problem. A customer did this and actually got charged more!! the $15 DID get calculated twice, but actually $7 did as well. which should not have. Attached is a final screen shot of the invoice. for $89 instead if $82