Numbers I have (from SAAB leasing) for a SAAB 340WT indicates about US$33,000/m for lease, plus insurance (about AUD$20k pa) plus maint and provisions (about USD$500/hour**).
Purchase prices are comparable to a B1900D but with 34 seats.
Fuel burn about 25-30% greater plus cost of Hostie (not just wages but training and C&T system and added approvals from the most feral part of CASA).
Assuming the strips and performance paramaters are suitable for both acft, on a route with growth potential you would quickly move into a cost/benefit grey area between B1900D and SF340B. Once you start using the SF340B the better product offering might just tip the economics out of the grey and into the black.
**maintenance costs are from manufacturer, in 2012 US dollars, and based on US$50/man hour which is a far cry from the AUD$120/hour you'll pay at an Australian Part145 org.
This is what I was getting at. The 1900 serves a unique purpose, and unless you really need it, it might be more sensible to look at something bigger i.e. SF340 or J41.
I haven't looked recently, but good, low cycle B1900Ds generally sell for as much as twice the cost of a Saab.