Beachbody, LLC, or Product Partners of Santa Monica) can proceed against you with a civil suit for copyright and trademark violations. The attorneys can seek payment of all money you received for the sale (and more if they can prove you knew or should have known you were selling counterfeits).
Innocent infringer? An "innocent" infringer can be pursued in a civil action but the penalties are often reduced based on the facts of the case -- that is, if the case were to go trial, a person in your position would fare better than the person who sold you the DVDs (and most likely knew they were counterfeit). In an ideal world, the attorneys for BeachBody might weigh your behavior -- lack of intent, cessation of sales and cooperation in prosecution -- and modify their demands accordingly. But in today's whack-a-mole world of intellectual property infringement, the business model used by your pursuers is to chase the small dealers, set examples for others, and hopefully recoup revenue to justify their pursuit. In many such cases, the judgment exceeds the person's ability to pay or may be pre-empted by bankruptcy.
Your course of action. If you can come up with the consultation fee for an attorney, we would strongly recommend you meet with one. There may be issues regarding your liability (including whether all the goods were counterfeit) and your cooperation that could merit a reduction in the proposed settlement. What you save with an attorney's intervention may justify the fees. (You may be able to get a reduced fee by dealing with a local legal arts organization.) If you can't hire an attorney, you need to make the strongest case possible that you cannot pay the $14,000 and try to negotiate a reduced penalty, perhaps with some sort of payment plan.