Informix to Postgres ...
I did a Informix to Postgres conversion for a branch of our state government.
IBM wanted us to continue to run Informix on a Mainframe at a cost of about 5,000.00 USD per month,
or by a 'Core' VMWARE license for 5000,000 - 1,000,000 one time plus maintenance.
It took me about a year to do the conversion and testing. About 230 tables converted, 80 functions and 175 triggers.
Did most of the work writing python programs to convert about 70 - 80% of the stuff for me.
Hope this gives you an idea.
From what the forums say, converting from Oracle to Postgres is not that big of a deal ..