Hey Jason - you can not setup auto-calculations for your custom fields, meaning you can\'t say Field A combined with Field B = $X.
What you need to do is combine those two fields into one and provide the different combo options in one custom field. You can then assign price values to each option combo.
I think I understand a little more what you are doing now. So, what I said really isn\'t the answer. You need two different calculation types... one for type of registrant and another for quantity. As you can\'t have one custom field be auto-filled based upon another custom fields selection, I think the best solution for this individual circumstance is to create 4 different events... one for each registrant type that you need. You\'ll need to setup manual links in your site to point people to the correct registration forms. You will now be able to put specific instructions/details above each form that pertains to that type of registrant.
Within each event, create your fee structure. You can make the custom fields now just to calculate quantity.
How many booths do you need? [dropdown with 0-10 for example]
How many attendees will you have? [dropdown with 1-20 for example]
For each of those fields, mark them as a fee field and input the price for each field option. Our video tutorial will walk you through this type of things too.