I found an article about construction cost that was done by Commander Michel Poirier on 20 Oct 1999. Here is what he wrote about construction cost and I quote.

German data used to determine the cost of submarines*(115). Where cost data on specific types of submarines could not be found (Type XIV, XXIII, Walter), he estimated the price based upon german submarines of similar displacment, accounting for difference man-hours. The exchange rate was based upon wartime U.S. estimates (he used $0.50 per mark, the 1942 estimate *(116). Of note, the cost of a U.S. submarine in 1943 was about $3 million *(117). The figures for German submarines are reasonable when compared to U.S. costs and man-hours required for construction *(118).

Cost - Type II, 52 boats at ($1.03 million) per boat. Type VII, 705 boats at ($2.25 million) per boat. Type IX, 194 boats at ($3.2 million) per boat. Type XB, 8 boats at (43.175 million) per boat. Type XIV, 10 boats at ($3.51 million) per boat. Type XXI, 123 boats at (2.874 million) per boat. Type XXIII, 59 boats at ($ 1.03 million) per boat. Walther, 7 boats at ($2.13 million) per boat

Only the costs of the 1,158 submarines completely constructed were calculated. The total cost was $2.76 billion.

Conclusion: The allies total investment was $26.4 billion to counter the the German submarines as compared to the German investment of $2.76 billion to build them. The allies spent at least 9.6 times the German investment.


References:

(115) - Erich, op. cit., German Warships 1815 - 1945, (Annapolis, Naval Institute Press, 1990), Vol. II., pp 40, 44, 68, 77, 85.

(116) - War Production Board, World Munitions Production, (Washington, D.C., War Production Board, Bureau of Planning and Statistics, 1944), p. 44. Much thanks to historians Timothy Francis (Naval Historical Center) and George Papadopoulos for this information.

(117) - Bureau of Ships, op. cit., p. 282.

(118) - Henry Davis, "Building U.S. Submarines in World War II", Processdings, (July 1946, pp.939.