The shipping costs for general products are calculated by this website, however, complete systems are near impossible to reliably calculate, so have their own “zero charge” shipping class.
What this means is that checkout will NOT charge you shipping for your order if you include one of these items. It will take your money for the item, as often these are unique items, and, once paid for, it can not be purchased by anyone else, however, you will then be required to make an additional later payment to cover your specific shipping requirements.
This charge will be at cost price only (my business is making and selling parts, not reselling shipping at a profit!) and packing will be without charge, however, you will be expected to cover any and all additional shipping costs in full.