My bust, I went somewhere south with my math, multiplied instead of dividing,but here are the parts:
1 10 ohm resistor, 25 watts from vishay electronics manufuacturer PN RH02510R00FE02 cost 3.07 usd. I have had good experience with Allied electronics in the past so that it where I would order that.
1 solar panel, 45 watt 90599-0VGA from harbor freight , I'm not sure if the unit includes blocking diodes so you may need to order a few 4 amp blocking diodes from allied to keep from discharging your batteries into the solar panel at night. Cost : a lot, around 250 usd.
A thermostat to save wear and tear on your batteries for the warm days. Find one that can handle about an amp an a half of load, say a replacement thermostat for a chicken incubater. cost somewhere around 20 usd.
Batteries, a good deep cycle will work perfect. Otherwise you are looking at getting industrial lead acid batteries.
Total cost: probably around 350-400. If you can get power to your hive, you can make this a whole lot cheaper.
Solar panel has blocking diodes installed, is then attached to battery. The panel should put out around 13.65 volts to charge it.
Run a pair of leads up to the hive, run one through the thermostat. continue on with your leads to the resistor, place one lead on each end. you will likely need to solder them.
A solar setup is likely more expensive than the hive is worth, along with the need to change out batteries each year, may make it cost prohibitive.
If you have household current you can do it a lot cheaper, and easier, and likely far more reliable. Think egg incubator control circuit. your basically doing the same thing.