what do i risk [besides obvious - cc number getting stolen] when buying ssl certificate for https use from one of many rapidssl resellers rather then directly from rapidssl ? disproportion in prices seem quite high: 10$ vs 79$ per year.
where's the catch? do you have any experience with any of resellers? thanks!
If it's signed by the same root, it comes down to the price and the infrastructure for purchasing (can you do it all online with a credit card, is it easy, etc).
You have to watch out for chained root certificates, where (someone like) RapidSSL signs a certificate, and that company then uses that certificate to sign yours. Unless you have a good reason, stay away from them.
I've bought certificates from Namecheap.com before - they will give you a single root certificate. See this question for more.
The risk is low in most cases, though I would recommend going with a company that either you personally have dealt with previously or one that comes with a recommendation from a source you trust.
For instance, most registrars also sell certificates through this sort of reseller agreement, and you'll most likely get the same price or not much more from them.
A short while ago NameCheap were offering a free SSL cert with every new domain registration which is where I got my last couple. You might find that offer still on, or that other registrars are offering something similar.
There is no need to go with a firm you have any reason not to trust, given how many out there resell at more-or-less the same price.
If cost is really the biggest driving factor - why not consider self-signing? It is super easy, and you can add the certificate to the trusted store for your browser - piece of cake for a small business or personal site. Granted, you won't get automatic recognition in a browser - but for cost, you can't beat it:
For Windows/IIS: SelfSSL.exe from the resource kit - http://www.microsoft.com/technet/prodtechnol/WindowsServer2003/Library/IIS/993a8a36-5761-448f-889e-9ae58d072c09.mspx?mfr=true
Apache: Just fire up openssl to generate your certificates.