I have found only Institut Francais which provides DELF exams in Warsaw, but prices in other places are rather the same.
ul. Widok 12
00-023 Warsaw
tel. 22 505 98 00
Prices for DELF Tout Public exams:
DELF TP A1 170zl
DELF TP A2 230zl
DELF TP B1 300zl
DELF TP B2 390zl
DELF TP C1 470zl
DELF TP C2 520zl
institutfrancais.pl/varsovie/2014/10/planning-et-tarifs-delf-dalf-session-de-fevrier-2015