It depends of the year, the kilometers, use conditions and special version (there are many Lancia Delta Integrale different versions).
In Italy the prices can go from 12.000 Euro (1992 years edition in good condition) to 30.000 and over for the latest version of 1995 with low kilometers.
It's not simple to find a Delta in very good condition becouse it's a sporty-car and many people use it on circuit or tuning It. But it still an awesome car and after over 10 years when a Delta go on the road people here say: "WoW! Look that great Deltone" (Deltone becouse in Italy we friendly-called in this mode the Evoluzione model)