For SUN, she hold Java Certification Day every Decemember. If you join, you can have 30% off discount on the vouchers.
For Oracle, Oracle Univerisity hold Summer OCP courses for University Students. You need to pay HKD $7311 for the whole courses, includes 40 hours lectures, ILT materials, and 4 exam vouchers. Since Oracle enforces a course requirement for OCP, this is a good idea to get OCP.
For IBM, she has given out promotion last year. If you paid USD $10 for each ICE test, and if you pass, IBM sent you a free voucher to take the real exam.
SUN and Oracle also give out beta exams. For SUN, all beta exams are free of charge. For Oracle, each beta exam costs USD $50.
Honestly, certifications do not help much in seeking jobs. It can help you to increase the chance for having interviews, but whether you can get the offer depends on your real experiences. Nowadays, employers wont recruit people solely becos he is XXX certified.
As I said before, my company encourages us to get certified, so she can sell to her clients that, her developers are certified on the latest technologies.
So far, I have only paid a little amount for those certificates and courses, as my company sponsers us around 70-80%.