Your benefit of using Wicket is about $2.5 million, according to the statistics I found while scanning the logs of ##wicket (freenode.net irc). These statistics have been provided by Almaw:

Total Physical Source Lines of Code (SLOC)                = 66,028
Development Effort Estimate, Person-Years (Person-Months) = 16.28 (195.40)
 (Basic COCOMO model, Person-Months = 2.4 * (KSLOC**1.05))
Schedule Estimate, Years (Months)                         = 1.55 (18.56)
 (Basic COCOMO model, Months = 2.5 * (person-months**0.38))
Estimated Average Number of Developers (Effort/Schedule)  = 10.53
Total Estimated Cost to Develop                           = $ 2,199,663
 (average salary = $56,286/year, overhead = 2.40).

Total Physical Source Lines of Code (SLOC)                = 9,781
Development Effort Estimate, Person-Years (Person-Months) = 2.19 (26.31)
 (Basic COCOMO model, Person-Months = 2.4 * (KSLOC**1.05))
Schedule Estimate, Years (Months)                         = 0.72 (8.66)
 (Basic COCOMO model, Months = 2.5 * (person-months**0.38))
Estimated Average Number of Developers (Effort/Schedule)  = 3.04
Total Estimated Cost to Develop                           = $ 296,172
 (average salary = $56,286/year, overhead = 2.40).