Dependent on size and quality you should be able to get basic models for as little as 40$ (e.g. the Instapark 5 head Solar Pump Garden). For a bit more (100$) you get better models such as the Solar Fountain 8 Watt Pond Water Pump.
Basic solar pond pumps generally come in a price range of $ 40 to $100 depending on the brand and performance. A search in the online shopping sites yielded the following price range: 1.3-watt Solar Fountain Pond Water Pump-$57.99; Instapark 5 Head Solar Pump Garden Fountain Pond -$39.99; Smart Solar Sun Jet 150 Fountain Pump 2 stars (4 reviews)-$69.99; Solar Fountain 8-watt Pond Water Pump Panel-$95.99
Yes, there are solar pond pumps available. You can find them at Pond Depot (http://www.pondepot.com/solarpondpumps.html) or Foster and Smith Aquatics (http://www.fosterandsmithaquatics.com/pond-supplies/solar-pond-supplies/ps/c/5163/14783). Amazon.com also sells pond pumps.
SiliconSolar, FountainFengShui and Pondepot all offer solar pond and solar fountain pumps and complete kits. Target offers a SunJet solar fountain pump for ponds at just $70. There are several companies that manufacture and sale solar pond pumps. One of the best in the industry,and the one I would suggest is Smart Solar.
Yes, in fact there are solar powered pond filters. This is a good idea to get, because it saves you money in the long run.
NaCl or MgCl
what is the climate on a pond
Who can say what an "average pond" is. - Have you done a survey of all ponds and found an 'average'.
You might buy a separate solar waterfall and Koi pond kit. Here are some good sources that sell the kits: WaterGardens.LumaGardening.com, ExoticWaterscapes.com and 123Ponds.com. You can also purchase pond kits at Target and Lowes. The Pond Digger Hybrid Koi Pond Kits from Exotic Aquatics is a good solar pond kit that meets the needs of a pond with Koi fish and your desire for a waterfall. You can call them at 800-522-5043 for a quote as they make the kit to your specifications. They have smaller kits that will also work and you can see them at http://www.exoticwaterscapes.com/pond-kits.php.
There are many brands of solar water pumps. Examples of solar water pump brands include Rule Rain, Smart Solar, Submersible, Wholesale Solar, and Dankoff.
A community around a pond. Alternatively, when a community is purchased, then sold for a lower price.
The average price of a good pond heater is around $35-$50. However, the cost for some pond heaters or deicers can list as low at $9 to $13 and as high as $1500. The higher costing heaters seem to be more specialized. Some of these heaters are made from titanium and others are used for keeping exact temperatures for koi ponds. Slight cost differences also occur between completely submersible pond heaters and those that are not. The completely submersible ones seems to list a bit higher than the others.
If the plant live in the pond then it well have water and sunlight so they will have some of thier basic needs
The first solar pond in India (6000 sq. metres) was built at Bhuj. The project was sanctioned under the National Solar Pond Programme by the Ministry of Non-conventional Energy Sources in 1987 and completed in 1993 after a sustained collaborative effort by TERI, the Gujarat Energy Development Agency, and the GDDC (Gujarat Dairy Development Corporation Ltd).