This is the most likely place to find promotions: https://www.vmware.com/learning/training/certification-special-offers-beta-classes.html
I doubt you'll ever find no cost options, other than linked complimentary items such as an exam voucher when you attend training.
Generally, the lowest cost options for VCPs are when you take training with a VMware IT Academy (if you're paying for it yourself rather than through a company)
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VMware Training & Certification blog
