Return value based on 2 dependent drop down lists

[arsene2conde]

Hello there,

I have been working on this spreadsheet for a while now and I am kind of stuck.
To provide some background info, I have a list representing pipe sizes with its description and cost, respectively.
What I have accomplished so far 2 dependent drop down lists. For example, the first drop down lists shows all the available pipe sizes. Once a pipe size has been chosen, the second drop down list shows the different options available for that specific pipe size.
What I am now trying to do is return the cost reflecting this pipe that I chose through the drop down lists.

Although I was able to do this, it only seems to work for one selection.
For example, I want to be able to add multiple drop down lists to show additional costs (1st row represents 1/2'', Copper K, cost and 2nd row represents 1/4'', Copper K, cost, etc.). I want to be able to add as many as I need (this would be used to estimate the cost of a new project).

I found a way to do this but it is very uneffecient. It requires me to add an INDEX function for every drop box I want to add (very uneffecient if one project requires 150 different items to be lsited while another one could only require 20...).
I am not sure if VLOOKUP could be used for drop down lists...

I was hoping someone out there could help me out, this would be extremely helpful!

Please note on the attachement, Reference sheet has all the backbone and formulas which is used for the Piping abd Fitting sheet.

Thanks.