Sadly, compared with 30 years ago, when I last bought one, prices have shot up. Here is a site with a complete system - 50W turbine, mast, battery, controller & inverter. If you use 12V LED lights, you would not need an inverter and you could have far more lights as their power consumption is a fraction of other lighting systems. Price is £840 for the full kit.
Alternatively, there are vertical axis turbines of similar power - in some situations, they may be the better option but tend to be more pricey - around £500 just for the turbine, without any of the other components, including the all important battery!
Very small wind is a challenge. To take advantage of your wind resource, a wind turbine should really be about 9m above any obstacle within about 150m (see http://www.homepower.com/articles/wind-power/design-installation/wind-matters?v=print, for example). With a very small turbine, the cost of the tower to get a turbine up this high can dwarf the cost of the turbine itself. If turbines are installed at lower heights, they are likely to fail prematurely from turbulent air, and will usually not perform well. Often solar electric systems are more cost effective, even in areas with a marginal solar resource.
But that wasn't exactly your question. For a good rundown of a number of home-scale wind turbines, check out http://www.homepower.com/articles/wind-power/equipment-products/2014-wind-turbine-buyers-guide. These are probably bigger than you would need, but will give you a good sense of what quality equipment is in this market, and their cost.
Some other potentially useful links:
Wind Empowerment: http://windempowerment.org
Right now I'm about to make the einfälle statt abfälle model. Just because it's the cheapest you can make, but it takes some work. It will give the power for some compact fluorescent light.
The einfälle statt abfälle's idea is to make the wind turbine from recycled materials ( a car alternator, a water pipe..., so on)
Another good option is hugh piggott home make turbines, better machines but more money, skills and work are needed.
I have build a few hugh piggott's turbines so if you chose that way don't hesitate to ask (not at all high tech turbines but they work for more that 8 year with really few maintenance). In both cases, the budget depend in your ability to reuse materials.
A small hugh one can go down to 500€ (let say 200w nominal power, including everything). Don't forget the tower because you'll need one and the materials there are not that cheap). In the einfaelle model we expect to expent 150€. But my partner is very good in finding reusable materials.
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