It costs you nothing and it helps me keep this site going.
Let me explain about the "Support this Site" vendor options that appear at the right on most pages and the Support this Site product links that appear at the bottom of many camera, lens, and accessory reviews and listings. Amazon is a vendor that I use regularly and can recommend without reservation. It provides access to a wide range of products and have very good service. It has established ways of arbitrating disputes and problems. And it has good pricing on things photographic.
Note: originally this site also used B&H links. Unfortunately, due to changes in interpretation of law, B&H has dropped that program in my state. If you'd like to read more on that, see my affiliate nexus overreach article.
The Amazon program costs you nothing but helps this site receive revenue. It's called an Affiliate Program, and all those links are part of that. Here's how it works: when you click on the logo or product link and you're taken to their site with an ID that's passed on identifying that you came from a byThom site (sansmirror.com is owned by byThom). If you purchase something during that session on either site, sansmirror gets a small commission. However, note that the price you pay for something from Amazon is always the same whether or not you started on my site or not, thus, you're essentially diverting a small portion of what you pay from the vendor to me, not paying more to support me.
Why do vendors do that? It's a form of advertising, basically. They're looking for continuous visibility on a high volume site, and are willing to pay a portion of their sales proceeds for that. The fact that they can directly track where their sales come from helps them better target their future advertising and marketing dollars. The extra links to their site helps them with search engine optimization.
Why do I do it? As I said, to help defray the costs of running this and my other sites. By making Support this Site links visible, I hope to generate enough revenue to continue adding new content to this site and eventually offer more complicated and time-consuming things I can't do now (e.g. videos). Heck, it might eventually allow me to hire some help that'll allow me to greatly increase the content of these sites. Unfortunately, due to changes in interpretation to Pennsylvania law, that is now in jeopardy, as almost no affiliate programs are still active in the state.
I've never allowed any other form of advertising on my sites, though I have used Affiliate Programs pretty much from day one on the bythom.com site. Long-term readers of bythom.com (and I mean really long term, as in back into the 90's and the earliest days of the Web), will remember that I used to have pointers to several other affiliate programs. Here's my promise to you: I only use vendors whose products and policies I can recommend for Support this Site, and I monitor complaints about them. If I get too many or the company in question changes their policies to be un-favorable to users, I remove them from the Support this Site links. As to those other Affiliate Programs I used to link to (other than B&H): the companies in question changed their policies in a way unfavorable to users (and I stopped using them for purchasing products myself), so I removed them.
I should point out that my recommendation of Amazon is only for the portion of Amazon that they perform themselves (look for "Ships from and sold by Amazon.com" in the Availability section of an item's page).
The Support this Site program is entirely voluntary on your part, and there's no other hidden relationship between me and the vendors whose links appear on this site. If you use Support this Site, I get a small percentage of your purchase price, and that's the only thing I get. If you don't use Support this Site, you pay the same price as if you had. So it's your choice. If you're going to order something from Amazon you can support me or not.
One small thing, though: you have to start your ordering from a link on this site and complete that order in your current session for me to get any money. If you put an item into your wish list, or you let your Web session with the vendor expire (usually after an hour or two), or leave something in your cart overnight, the affiliate link is dropped and I get nothing.
Meanwhile, if you have a problem any Support this Site vendor, I'd like to know about it.
Thanks for your support. It really will help me make this site better over time.