From what I have seen suppliers are not dependable to deliver what was paid for. I cannot recall once seeing a post here about a customer not paying. I have seen at least two threads, one covering a span of years about suppliers not delivering.
I have also lived in the reality of what collecting payments is like. I would say a good 50% of customers will receive notification that a product is ready to be shipped and they will delay payment by a week or more. This would never work where bees are concerned.

My paying for anything up front would have everything to do with the reputation of the supplier.