If I may respectfully suggest to the forum, that the "grinders" you are referring to are not, in truth, grinders at all.
The small whirly blade items from breville et al are share their mode of action with the standard blender or food processor.
A proper grinder has two surfaces that crush between them. Also called milling.
I'm only pretty new to brewing but have been in the coffee game for a very long time. The advantage of milling over chopping is the consistency of the end product - that is, you can set your grinder or mill to produce a flour (grind) that is any desired grain size.. In a blender you can not.
In an environment where control over grain size is crucial (coffee) a blender will never give results in the same ballpark as a grinder, even a cheap one.
I'm not enough of a mash extraction expert to know how consistency of the milled grain size affects sugar extraction, but I'd hazard a guess that its not as big a deal.
Dont take this post as a criticism, please. I learn so much each day from you guys. But my inner pedant couldnt read "grinder" when I saw pictures of blender.
PS a Sunbeam EM 0450 for $149 will smash thru grains on a coarse setting all day and only stop when you stop feeding it.