It varies, depending on a number of factors. How large is the property? What condition is it in? And more specifically, how long will it take to clean?
The way someone SHOULD price a cleanout service is by first determining how long it'll take. Let's say it'll take 20 hours. Obviously, that depends on size and condition of the property.
The second step is to calculate the value of your time, or the time of the people who'll be cleaning it. Let's say you value your time at $15 an hour.
You multiply the time by the labor rate. In this case, you'd come up with $300.
Then you add in overhead. That's the time you have to spend getting a job, as well as the paperwork and other non-revenue items. For many cleaning-type services, direct labor is about 70% of the total charged. So about 30% is overhead. So, adding in overhead, you're up close to $400. Your overhead will vary, but don't underestimate it.
You might want to adjust your numbers up a bit, depending on market conditions. Never adjust them down. You'd be cheating yourself--working for less than what you've determined to be a fair hourly wage, or working extra hours for free. Don't do that. But let's say, in this scenario, you're at $400. How urgently does the property need to be cleaned? The price might go up some. Or how busy are you? If you're already stretched thin and you'd have to squeeze this job in, or hire extra bodies at above your average rate, the price could go up.
That's the basic approach.
Here are a couple of additional resources:
Hope that helps.