Controller for smart greenhouses

For a smart home there are a lot of solutions, I think it's time to expand into the garden.
I propose to discuss the project controller for a smart greenhouse.

I will add that all of the following are separate devices that are not always compatible with each other, but we need a single system that does not require the fitting of components.

Here is a sample list of what you want to see in the final device:
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Stage I - basic functionality
At least 8 channels for sensors (air humidity inside, air temperature inside and outside, soil temperature inside and outside, air temperature in the ventilation channel, illumination, 1 reserve);
Display of sensor readings on a large LCD display (LCD and touchscreen are also possible, but this seems to be much more expensive);
Control of actuators:
-Opening / closing of watering cranes and bay barrels according to a given logic and sensor readings;
- switching on / off the fan (both in one and in the other direction) according to sensor readings and logic;
-the inclusion at night of two channels of LED-lights of plants (blue and red spectrum) in a different ratio, according to a given calendar.

Stage II - possibly in the form of a separate plug-in module, because not everyone needs
Work with a SIM card:
-the receipt of current information about the state of affairs (sensor readings) by SMS;
- notifications about critical situations for several numbers;
- device control commands via SMS;
- transfer of data via GPRS / 3G (for the next stage).

Stage III - buns
Web interface or application for Android:
-the receipt of current information about the state of affairs (sensor readings) by SMS;
- archive of indications, schedules;
-control devices through the interface;
-change settings and logic;
-web camera or snapshot;
-the weather forecast for the coming days (widget).

Initial power: 12V (car battery, charged by solar battery by an independent controller).
The platform is the Arduino / RoMeo / Rapsberry Pi / something similar , because the market is full of more or less standardized sensors and actuators ...
Climatic conditions: from -25 to +60, from humidity can be hidden in a sealed industrial box.

How much can development of such a controller cost (in fact, more programming, because there are a lot of standardized sensors and actuators now)? If without greed?
Maybe there are controllers of “smart houses”, where all this has already been implemented, just sensors and executive devices of another purpose?

I think at a price of up to 5 thousand. Such a controller would also sell well, which will pay back the initial investment.