When we renovate our home there was no quote item for so-call 'design fee'. However, I would suggest that you should consider the entire quotation as a whole instead. I would think that even for firms who do not have the quote item for 'design fee', they can also add-in the cost of it into the other items in the quotation 🤔
It might be a better comparison if you were to compare the provides items between multiple quotations against the final cost of the quotation.