You can buy an excellent DOCSIS 3 modem for $85-$100. It's more expensive up front. But the longer you keep the modem, the more you save. I know people who have had the same modem for 6 years or more.
The downside is that you're on the hook if something goes wrong with it. Plus, you're responsible for staying current on firmware updates. However, those don't happen too often.
If you decide to buy, check out your service provider's support pages for recommended DOCSIS 3 modems. If you stick with top brands such as Motorola, Zoom, Linksys and D-Link, you'll get reliability and a good warranty. You should also be able to use it with another provider if you move.
When shopping, you'll notice some modems with built-in wireless routers. These are often called gateways. While a gateway is convenient space-wise, it has disadvantages.