Following a general weakening of economies world wide and the crash of the US Stock Market in 1929, the GREAT DEPRESSION struck with full fury, with many millions of people laid off or simply fired and many thousands of companies world-wide shut down, sold or liquidated.  Purchasing of portable typewriters, as one might expect, plummeted but the manufacturers in some cases reacted and produced less-expensive machines intended to help boost the "bottom line" and at the same time provide machines people could afford.  Here is a brief look at a few of these machines.
Remington-Rand produced a number of machines with few, or no, options and had the luxury of producing more than one basic size of portable.  Among the smaller machines are the well-known lower price "Depression" machines such as the Cadet, at left, and the Monarch Pioneer, at right.  Both were priced under $20.00 when offered.  Both were sold in the late 1930's.
The Monarch Pioneer is obviously branded as a "Monarch" although the original company by that name, and any separate hierarchy, were long gone by October 1937 when it was introduced.  Only about 17,500 were made before it was withdrawn in June 1938; Remington-Rand ordered the stock closed out later that year, in October.  It seems that the Cadet replaced the Monarch Pioneer seen here.  The Cadet is labeled as "a Rem-Rand Product" which is a bit closer to indicating the actual maker.  Note the three-and-a-half row keyboard on the Monarch; note also the lightweight, small frame of each.  Very light covered board cases were available which had no hold-downs or latches of any kind to secure the machines.  (Original data from Chuck & Rich / Richard Polt.)
The Remington products seen above are considered by some collectors as uninteresting since they essentially contain a key lever / type bar mechanism very like that of the large, heavy Remington portables of the day and are simply made of light metals (the type bars on the Pioneer above are high-granularity pot metal) and are thus not mechanically aberrant.

The Royal Signet seen at right is thus more interesting since it is "aberrant."  This machine matches other Royal machines in almost NO way.  The style of body, the key lever / type bar mechanism, and most other features just aren't in common with anything else in the Royal pantheon.  It is sometimes speculated that the Signet (seen here) and the Signet Senior (not shown, similar and can actually type upper and lower case) were the design of someone outside Royal, perhaps another company, and were bought by Royal for use during the Depression.  Just like most other true Depression machines, this Signet has no back-space, no margin release and is just an absolutely basic machine.  Again, note that it types capitals only.
Tilman Elster provides a picture of an Underwood offering of the day.  This is an Underwood Junior; it is quickly recognizable as such because of the total lack of auxiliary keys like backspace or margin release.  Its body is simple, color black.  Simple carriage with no paper bail and simple paper fingers with no rollers. 

Royal did in fact make a somewhat similar machine -- the Royal Junior.  It was basically similar to the Royal portables of the day, but devoid of options as is the Underwood Junior seen here.  NOT that the Underwood and Royal machines have anything to do with each other; they do NOT.  The point is that Underwood offered essentially one concept for lowering price -- stripping down its basic machine, while Royal offered two concepts -- both a stripping down of its basic machine AND the addition of a previously unseen and exceedingly simple and inexpensive machine to augment it (the Signet line seen above.)
In 1934, LC Smith & Corona began to offer the Corona Junior, seen here.  This machine was quite like the Corona Four offered at the same time (the body styling was new in that year) but was stripped down greatly in options and features.  At the same time the company had introduced a much larger, heavier machine (the Sterling / Standard / Silent line) which didn't initially sell extremely well; the Corona Junior, with a small variety of sub-models and the folding Corona Special did sell fairly well for a couple of years until the economies recovered - at which point the large portable began to take off.

For all intent and purpose, by 1940 all of the "Depression" machines were gone, replaced by newer models, modified or just dropped.  The world was about to experience more change, in ways it hadn't imagined, and the industry would change as well.