ref acmi operation
for a wet lease acmi expect to pay block hour around 3800-5000 usd for a 200 and between 5500-7000 usd for a 400.. availability on pax 400 for one month severly limited. main issues are co insurance which can be expensive depending on your destinations
and registery as all leases nowadays for a period longer than 5 days require filing with the aviation authorties of the countries involved..
best package is also to ask the airline to include in the BHR all positioning depositioning hotac and off air airport transport costs
this will save a lot of hassle on sorting out crew costs later
good luck..