Spidey knows me too well - I live and breath load balancing, proxies and web traffic flow.
A SSL certificate is assigned for the hostname of your site -
www.mysite.com. If each of your app servers (which are, I assume, really a combo web / app servers) responds to requests for
www.mysite.com the same cert can be installed on each of them. Depending on your SSL certificate provider (Verisign, thawte, etc.) they might or might allow you to pay for a single cert. I believe that some (i.e. verisign) requires you buy a cert PER server, not just one cert for the site. With a load balancer, there's only one device terminating SSL, so only one cert.
Look at the costs. If you have to pay $500 for a cert for each server and then add either new servers or SSL accelerators on the existing ones, the $$ adds up. Run the numbers, figure out the two-year cost and see what it's going to cost to do it WITHOUT offloading it onto a load balancer.
Look around at ebay and see what you can find used. Before you buy, however, talk to the vendor to determine what kind of strings there might be. i.e., F5's warranties AND software licenses are non-transferable (accoriding to our rep). You might get the hardware, but might never be able to get support on the box since you don't officially own the software.
- G