Brake replacement on a 2012 Honda Civic expensive?

I have 2012 Civic that has close to 51 thousand miles. When I bought it it had 48 thousand. I doubt the brakes have been replaced as I have already replaced the tires. But when I'm braking I feel like I have to slam my foot on the brake. I have no brake warning lights in the car letting me know if thats an issue so ill just get them replaced. It has front discs and rear drums. Will it cost like 100 bucks?

Heck no. $100 would cover one hour's labor only.

To get just the fronts done (new rotors and pads, with labor), you're looking at about $300. Rears can be done for another $150.

Just over $20 each for front rotors, around $20 for both sets of pads… Do it yourself.
Add $25 for a manual, or get one from the library.

There's probably meat left on the brake pads, but if you feel like changing them, read up on the job or watch a YouTube on it. Put anti squeal compound on the BACK of each brake pad before you put it in and get all the shims in place so it doesn't squeak. It's a good idea to flush the brake fluid to remove any condensation it may have attracted. A shop will probably charge you $250- $300 to do the brakes. If the wheels don't shake when the brakes are applied, don't worry about the disks. If your rear brakes are drum brakes, do not put any grease on the brake shoes, but clean every moving part, and be sure to adjust the parking brake.

Having to slam on the brakes often indicates driving too fast or being inattentive. If the brakes are spongy, there may be air in the brake lines that needs bleeding out. Try that first and look at the pads and shoes to see if they are worn out. If you have 4 mm or more lining, you can leave the job 'til next spring.

You can get the pads and shoes for around $50 at AutoZone. Genuine Honda parts will run quite a lot more.