I believe the rebate ended in July. I can't find any current rebates on the Berkley website.
I did buy some PowerBait plastics and Trilene line from the website on sale earlier this year and then used their rebate to make it nearly free like you are suggesting. I have already received and cashed $20 in rebate checks.
All I know is that I purchased 12 bags at 4 for $10 and I received 3 rebate forms printed out from the register for a $10 rebate per 4 bags with a limit of 4 rebates per person valid on purchases through 9/2/2017.