DWs are great Revolvers...
with narrow customer demand.
The concept of barrel changing and or caliber conversions on just one frame is a good idea for those that are restricted by the State to owning one pistol only. The idea never really caught on in America. An example would be the .22RimFire conversion for the 1911 .45acp, or the .22 RimFire conversion for the AR-15s. Finding them rarely used, inexpensive and still in great condition is common at many gunshows.
If memory serves me correct, in the late 1970's a DW with 3 or 4 extra barrels along with the little tan suitcase with red cleaning rod, was more than twice the cost of a new Colt Python or wood cased S&W Model 27. H&K had a Walther PPk size pistol with conversions for .22LR. .25acp, .32acp, and .380acp., magazines were extra. Eeewww.
I worked a second job for about a year and had to settle for a 6'' blue Python and Walther .380 PPK. Darn if that H&K didn't come in a cool looking box.