This replacement toothbrush heads 16-pack is priced at $9.99 on Amazon, but you could pay as little as $2.99 with this deal.
Use Subscribe & Save for 5% or 10% off. Then clip the on-page coupon for an additional 10% off, and then enter code 4DLNMR5L for 50% off at checkout. This will bring your final price to as low as $2.99.
Note that these brush heads are for select Oral-B toothbrushes.
The next time you're getting something this cheap, make sure to earn free Amazon promotional credits so you can get it almost free. These Amazon credits are easy to earn, and you can use them on just about everything.