This seems to be a widespread experience. I've heard the same said of a number of RIB manufacturers and it often puzzles me. IMO, it is a result of "issues" on both sides.
On the manufacturers side, if supplying customised craft to order then pricelists are going to be a problem - i.e. a meter of bare Humber is going to look very cheap compared to a meter of finished Ribcraft. Also, I suspect that some builders are not particularly "sales" minded and their "sales resources" can be eroded during busy production periods.
From the customers side, I know that email enquiries to boat builders can be a mixed blessing. Anyone who has sold a secondhand boat can attest to the number of dreamers out there. Builders get these too. An email enquiry that takes a minute to write can take 30 minutes to answer. I make this point only to indicate that email inboxes are like ore - they need to be mined and processed to yield gold. This takes time and some skill. Sometimes paydirt gets missed.
To return to the OPs email requesting a pricelist - I can't imagine how any business thinks not replying is a good thing. But it happens and it happens often. My business gets similar enquiries every day, some are one liners in lowercase without punctuation but we treat them all seriously. My team filter them as they come in, deleting the spam, dealing with the simple stuff and passing on the leads to the sales team. Where we get very general enquiries that cannot be answered easily and quickly (in RIB terms "how much is a bote?") we reply politely thanking the sender for the email, provide some but EXACTLY NOT ENOUGH information and ask them to provide a phone number so we can give them a quick call at our expense to discuss their needs in greater detail. They feel wanted and it saves us hours of work. It also increases sales conversion rates. I have someone on the team who reviews sent sales emails to ensure that this process is adhered to.
I have noticed, in my own business and in others, that if individuals who are involved in Production are allowed to deal with Sales, then the likelihood of a sale is diminished...