Hello,
I've been working with Postgres and MySQL for about 4 years, and with large datbases. (See Openbravo in my CV)
If the app needs changes in the sources, I think those changes are not included in my cost estimation,
If you want to discuss more details, please don't hesitate to have a talk or chat with me.
Kind Regards,
Edwin Martínez
Quito - Ecuador
Skype: edwin_mn