The cost of an LLC depends on a few factors. Are you doing it yourself or are you hiring someone or a company like LegalZoom to do it for you? The cost will also depends on the state you are registering with.
To first register the LLC you may pay around $100 in many states, and then around $100 once per year to keep the company active with your state. However, do check with your state before seeking (specifically paying) for advice, because some states like California require a minimum of $800 each year for special taxes.
Be cautious on who you go through, since some places charge a hefty fee or fees that can just be avoided to begin with. LegalZoom has packages that charge $79 for an operating agreement and $59 in addition to file for an EIN (Employment Identification Number). With only a few moments of your time, you can get the EIN yourself, and there will be no fees to pay.
What about Extra taxes you have to pay as an LLC? Aside from select states like California, the only extra money you have to spend on taxes is the small cost to register the business and to keep it active. There are no special federal taxes you have to pay just because you are now an LLC as opposed to an individual owner. The only time you may have to pay more taxes (and in some cases less taxes) is if you request the IRS to treat you like a corporation on your taxes.
This cost can be slightly higher though since you need what is called a Registered Agent. You must consider if an LLC is within the budget with your specific scenario. A registered agent can be yourself, however, whatever address provided must be an address where someone has agreed to sign for packages and is at the address during typical business hours of your state. If you or an employee are in the office during these times, then the cost can be zero. If you must pay an outside provider then do your research. While LegalZoom may charge you $399 each year to be your registered agent, ask your local accountant if they have that as a service because many provide such a service free of charge. Otherwise, your lawyer or any local lawyer should have such a service at a much cheaper rate than LegalZoom. Keep in mind though, with lawyers it is typical practice to have to hire them on retainer. Meaning you will prepay for future services.