There are two kinds of M38: one made from a M96 rifle cut down (commonly called the M96/38 by collectors), which will be made by Carl Gustaf or Obendorf, dated 1898-1938, and will have a straight bolt handle; and one purpose-made as a carbine by Husquavarna, dated in the 1940's with a bent bolt handle. The "M96/38" is much less common, and in my opinion more interesting as it comes in more varieties of date, stock wood, etc. The "Husky" will be found in much better condition - which is what I assume is the "new, unissued" M38 in question. Forgive me for this, but the Husky is worth about as much for the basis for a sporterizing project as for a collector piece, given the bent bolt handle, the great 6.5x55, etc.
As suggested, they will be worth less than $300, even for VG+, most falling into the $200-250 range. Add as much as $50 if it comes with a range plate, $50 if it's an Obendorf, $50 if the stockwood is rare (Elm or Maple, or "Tiger" Walnut), but I can't see any M38 being worth more than $400.