You can work out what value you are getting per point by dividing the seat cost in cents minus the tax (in this case 23900) by the cost in points, in this case 12000. So for this particular seat you would be getting 1.99 cents value per point.
As others have mentioned only you can decide whether this is worth it for you, taking into consideration various things such as what it cost you to earn the points, what your cash flow currently looks like, whether the lost opportunity to earn status which comes with the revenue fare matters to you. Also it's worth asking whether the $299 is a sale fare with restrictions on refunds and changes or not. IMO, one of the big benefits of award seats is they are very flexible and almost fully refundable very close to departure (minus a points fee).
As an aside like many here my preference is to save points for international J class flights where you can get much higher value per point.