I have an extended analogy for this issue. Bear with me.

Consider the price of the most expensive automobiles produced on a large scale: something in the area of $200k. There are cars more expensive than this, but they are made in extremely limited numbers, and thus don't really fall under the category of large scale production vehicles.

Now, consider the price of wrist watch in the same echelon; you're looking at about $10k. Again, much more expensive wrist watches exist, but in severely limited quantities.

This gives us a price factor of 20x when comparing market values of cars versus wristwatches. If we apply this to mid-range vehicles, let's say $30k for a mid-range vehicle. Apply the factor of 20 to this, and the mid-range wristwatch comes in at about $1500. Sounds about right, right?

Now consider a wristwatch that, brand new, costs $150. You're looking at the equivalent of a car that sells for $3000 off the showroom floor. Does that sound like a car in which you could be confident of the quality? Of course not!

The only reason wristwatches this low-end exist is because, unlike cars, wristwatches are not necessarily a mechanical, or electro-mechanical, device that allow checking the time; they can also simply be toys. Therefore it's safe to conclude that the price of the cheapest production automobile (about $10k), divided by our factor of twenty ($500), gives us the price of the cheapest production wristwatch which would be suitable for use as a primary method of checking the time. Any wristwatch under that $500 mark can be assumed to be designed for use as a toy.