So you're handling mains in the product but have no other mains derived voltage rails?
If you have something like +/- 48VDC, 24V, 12V, whatever you can just buck or whatever that isolated rail to get 3.3VDC but I guess you don't have such handy. Even going from a 350VDC PFC output rail through an isolated converter is another option, whether it saves any layout / cost issues can't be said generally.
Also for other parts of the system there are other online design wizards like TI's Webench that will design a lot of power conversion stuff for you as well as a few other things and produce BOMs, budgets, layouts, schematics. I'm just not aware that TI has isolated ACDC switchers like ON / PI do. Well I know TI does have some ACDC application switchers after all they bought Unitrode that made some of the classic ones, I mean I'm not sure of what they make at the moment that is most relevant for your design as well as having WEBENCH support. You can see if anything comes up as a sane solution from TI as well.
Fairchild has online tools of some sorts, and so as I recall might Infineon who do make stuff for ACDC and DCDC applications too.
Almost worst case budgetary would be to look at the costs of COTS ACDC isolated power modules from the likes of CUI, Vicor, TDK Lambda, whoever is selling them on Digikey / newark. That would be a drop in solution more or less, but more costly than self-made.