Yes that's one big reason people buy from Amazon: rack up all those 'points' using the credit card, and things are "free".
It's worth noting that AFAIK there are three types of sales "on" Amazon:
1) Purchases *from* Amazon. They sell you the item, and it comes from one of their warehouses.
2) Purchases fulfilled by Amazon. You are actually buying the item from another seller, but it comes from an Amazon warehouse and is delivered by Amazon either directly or by UPS or USPS.
3) Purchases *through* Amazon. You pay Amazon, but you are actually buying it from someone else and it comes from their store or warehouse, not from Amazon.
You can tell which category an item is by looking at the "Sold By:" and "Ships From:" fields if you pul up a list of sellers for an item.
Note that (3) may not have the same delivery or refund terms as (1). (I think (2) does.) For example, if you look at some of the current listings you may get two-day free delivery but it's not coming from Amazon. Some of them offer free delivery but it will take longer.
I just looked quick (so might have missed something) but ALL of the SDS100s for sale on Amazon fall into (3). Amazon charges your credit card, but you are actually buying from a third party and it will be shipped to you by that third party.
I think someone already mentioned that Police Scanner Outlet is the Amazon persona of Bearcat Warehouse. Webtron-x is also a real store that sells scanners and other electronics. So you can still support a "real" scanner vendor but still go through Amazon.