Hmm. here are the full conditions. Looks like you need to purchase it at the full $399 price. Maybe someone was able to get it to work, but I don't want to chance it.
Reduced pricing based on purchase of PS3 at the $399 MSRP for 80GB. Does not include tax or shipping and handling fees.
1. PlayStation Card is issued by Chase Bank USA, NA, and is subject to credit approval. To qualify for this offer, you must apply for your new PlayStation Card by 12/31/08. In some instances an application may require additional processing, in which case instant approval will be unavailable. To qualify for the $150 card credit, you MUST purchase a PLAYSTATION 3 system with your new PlayStation Card ("PS3 Purchase") at an authorized Sony retailer such as Sony Style store and SonyStyle.com. Complete instructions will be sent upon your approval for the PlayStation Card via email. To receive card credit, your account must be opened by 01/31/2009 and PS3 Purchase must be made by 03/07/2009. Card credit will be posted to your PlayStation Card Statement within 8-12 weeks after PS3 Purchase. This promotional offer is available to new PlayStation Card accounts only and only one $150 card credit may be earned per PlayStation Card account. Existing PlayStation Card account holders or accounts are not eligible.