Just a note about distributors.

It can be very, very hard to get 1 or 10 units from a manufacturer, unless you have the contacts and can get them as samples.

A number of distributors are interested in selling 1 or 10 units even if they know that you will not buy more, just since they are distributors for other products too, and wants to build a personal relation with you. They may loose out on one product but instead land a very pleasing deal later on for another product.

I don't think the mediating people add any time. I have received pre-production units from quite a number of brands through distributors. The big distributors have anohter advantage. They can put you in the VIP chair when you need to get your questions forwarded to the manufactorer. Trying to initiate a relation directly with the manufacturer can be evilishly hard unless the distributor have taken the first step and arranged the first contact. A big distributor is extremely important for the manufacturer, so if a distributor complains that the support isn't good enough, the manufacturer will listen - or possibly loose half a continent of sales.

Another thing: If they component in question is in high demand and the manufactorer gets into troubles to produce enough, a distributor you are in good favor with may help you get your orders prioritized. I have many times worked - or produced pre-series batches - with components where web forum posts all around the world complains that the components can't be had even in samples. You might even have situations where a new chip has a known errata. The manufacturer refuses to send out the chips generally even in samples because of the badwill from unhappy customers. But with good contacts, you may come to the conclusion that the errata is not relevant for your specific product, and the distributor may help you get your hands on the components anyway. Being able to run a 100-unit prestudy during the three months the rest of the world waits for a fixed stepping to be available for production may mean a lot. If you can manage that directly from any of the bigger chip manufacturers, I must say that I'm really, really impressed.

Building a good relation with the distributors also helps when you are about to redesign a product or design a new product. They can help out quite a lot looking for suitable components. Besides picking up the general "what is everyone using right now", they also get a lot of preliminary information from the manufacturers - information that you would be hard-pressed to get your hands on on your own.

In the end, few big manufacturers are willing to sell to end users or have online web shops (except the web shops where you need a distributor password to log in and where they sell in bulk). Most of the products you do find online from the manufacturers are designed and built by quite small companies. The products may be very, very good, but often they have to charge quite high prices since they are not big enough to get (or even being able to handle) the really big orders and they need to cover the work costs when their average orders are quite small and requiers lots of work/shipped unit.

The big advantage with this kind of manufacturers is that you can call them and ask them to deliver 500 units with a custom modification and they will be interested. The disadvantage (besidees the higher price) is that you can't know if they have the economic engine to manage to maintain their products and perform all the testing and get all the approvals you would like. If you sell 500 units/year it can be economical to drop the product if a component becomes obsolete. If you buy a similar product from a company that sells 50k units/month, that company has a big economic interest in keeping this sales volume - the cost of the redesign will be so low compared to the profit of the product.