At my local hardware store (Jula), there are electric grinding stones in all price categories from NOK 250 to 3 200 (USD 32.50 to 416). I paid NOK 1 500 (USD 195) for mine. Why this price difference?
Depending on your worldview, the Rolls-Royce, Maybach, Cadillac, Zil, Toyota Century or Trek (yes, the bicycle) of the grindstone world is Tormek, a Swedish manufacturer. If you want to be convinced that one should spend more money on a whetstone sharpener, there is a YouTube video that explains everything, Why does the Tormek T-7 and T-4 cost so much? Interview and review with Stig from Sweden: https://www.youtube.com/watch?v=ESW3wy0PI18
Not being convinced, I opted for a Scheppach TiGer 2000 S, which looks like a plagiarized version of the Tormek T4. The T4 is undoubtedly better. One person suggests 20% better, whatever that means. It also comes with a 7 year guarantee.
While larger diameter grindstones are preferred to this 200 mm machine, because they provide a larger concave grind on edge tools, these larger machines also need a more powerful motor and housing, making them more expensive.
While the unit comes with both a straight jig and an angle guide, some users may want to invest in a wheel dressing jig to flatten/ true the stone edge. Specialist jigs are available for knives, woodturning tools, axes and scissors.
Mount the stone wheel and plugging it in, is all that is needed to set up the machine. The metal shaft is strong. However, the sharpening jig fits loosely. Many reviewers have commented that a Tormek jig is much better. The 120 W motor is more than adequate. Most tools can be ground adequately. The leather honing wheel is also adequate.
Note: The first three paragraphs of this tidbit were originally written: 2018-03-18 at 07:15:29 with the title Workshop Tools: Whetstone Sharpener. Since then it has been waiting for further inspiration, that has never arrived. On 2020-03-08 at 23:00 the text was edited into blocks using the new(ish) Gutenberg block editor, rather than the Classic editor used in 2018. The title was changed to Whetstone Sharpener: A tidbit. The last three paragraphs were added, along with an illustration of the Scheppach TiGer 2000. Prices in NOK were identical in 2018-03 and 2020-03. However, the Tormek had increased its price to NOK 3 800. In 2020, 1 USD is worth almost 10 NOK, this will also influence price comparisons.