startssl covers the cost of their labor, not the cost of a 'license' to use the certificate. Their cost is validating your identity, which is a one time thing. They call you, ask a few questions and that's it. 10 minutes of their and your time. After that you are entitled to create as many certificates as you want. There's one caveat: the validation is only for one year, you have to renew it when your certificates are about to expire. Even if you have just one domain, it's cheaper than the alternatives. If you have multiple domains, startssl is much cheaper.