What kind of survey? I ask because if it's photo the Turbine exhaust plume effects the quality of the photos. If you don't need pressurization how about a Soloy 206. There is a nice Mk 1 for sale in Australia for under $500K and a newish Mk2 in the states for $845K.
M & O operating cost for the Rolls engines is under $100 per hour fuel flow 26US gph.
Contact
www.soloy.com for details.