Operating cost is not a function of weight. It is a function of MTBF, the cost of components installed (repair/replacement), and fuel/sundries. Maintenance per flight hour can also be added on.
139 is same or less DOC's per hour, than a 76C++. CHC proved that over and over. Yet the 139 is heavier.
145 Max range, NO reserves is 365Nm. IFR with reserves takes it 300 or less. So for EMS, 150 out, 150 back.
169 is close to 400Nm range, with reserves.
Amount of fuel carried and consumption per hour is only part of the story. Speed is the other. Most AW's have their economy cruise in the 140-150 knot range. EC145 economy cruise is not that high. Hence 169 goes further.
Oh, it is cheaper too, by over US$1 million.
Ask FAA how long it takes at the moment to get an STC approved and you'll begin to understand why a Type Cert is taking so long, even though it is EASA certified already.
For STC's it is quicker now to do it in Canada and get it recognised through the bilateral agreement, than to do the STC in the US. Perhaps Leonardo should have certified the 169 in Canada first, then applied for the US certification!