That will be a red flag for me from the start. hardware service providers, consulting firms, and auditors making money on naive Western entrepreneurs are quite often big crooks themselves.
It is the same story with companies in financial space being forced to pay 10x premium to get just anything done on software front because they have near zero internal expertise, and they have no alternative to following whatever crooked colluding consultants say them to buy.
If you were homed on the moulding factory by a consultant, there is a big chance that he himself was in share with them.
I myself, I never had any issue ever on that front. Never place the whole order. Look for mid-sized contractors with a track record and cultivate your own relationship with them. Prioritise ones with shorter lead times, and ones pitching on their ability to handle design changes, and expertise on work with different materials.
The paragraph above is what people in Shenzhen charge $1000 and more in consulting fees (hourly.)