Back in my first startup where we were accepting credit cards, we purchased an SSL certificate in order to assure our customers that their credit card information was being transmitted securely.
We bought that SSL certificate from VeriSign for $495 per year. That was 2003.
Nowadays, you can get an SSL certificate for around $50. With the explosion of SSL providers and resellers, there are bargains everywhere. Last year I purchased a certificate from RapidSSL for $49. You can find the same certificate at wide range of prices from different resellers, from $15 to $79.
Does it work? Yes. It's an SSL certificate that supports Strong 128/256 bit encryption, which is industry standard SSL.
And compared to the pain I went through with VeriSign back in the day (faxing documents, letterhead, etc) it's a savings of time, too. With RapidSSL there's a pretty fast verification process and you're done.
"But I found this other certificate that's cheaper." Great, buy it. Like I said, there are many providers and each has many resellers. But if you're looking to save $5 by going to Stinky Ralph's Discount SSL Certs, I don't know about that. Use your good judgment.
Update (Jan 31, 2016): I recommend ClickSSL nowadays. The certificates are less than $15/yr. If you need a wildcard certificate, they run about $130/yr. If using Amazon AWS Elastic Load Balancer, they now provide up to 10 free certificates for your load balancer.
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