-sigh- Alright, a lot of you don't seem to understand how software, or software development works.
The simple answer is that a PS3 version of FFXIV will ONLY limit the amount of content that can be produced because of the extra workload required to develop for two platforms. When they make changes or add new content, it will need to be tested on both systems, and sometimes developed separately (though most things, like models and items and such will only need to be made once). New content development will just take a bit longer than it would if this game was PC exclusive. As a tradeoff, you get a larger player base which means more activity and people to play with (what's an MMO without the people?) , Square-Enix making more money because of the larger player base, which in turn will hopefully fund even more content for the game. Thus, in the long run it will actually be a GOOD thing for FFXIV.
Hardware limitations of the PS3 vs PC have nothing to do with it. It's extremely easy for them to limit graphics on the PS3, but fully "unlock" graphics on the PC, allowing you to achieve the highest fidelity if your PC can handle it, while still having the PS3 perform smoothly. Though some content development may take a little longer due to having to develop it for two platforms, most of the content will still be just as easy (not counting testing). Creating a new item is simply a matter of filling out a database entry and/or dropping/linking a new model and texture file into the correct directory. Same with new monsters and NPCs.
Your logic is flawed here.
The thing is, you cannot directly compare a PC graphics card to a console graphics card. They work differently.
When a developer makes a game for a console, they can develop and code the graphics specifically tailored to THAT hardware. This is a HUGE advantage over PCs. You can optimize specifically to the PS3 hardware, and don't have to interface with drivers the way a PC has to. This essentially gives you MUCH more bang for your buck in terms of power vs graphical fidelity.
While on the PC side, the developer has no clue what his/her game is going to be played on, so they have to develop in mind for all cards. PC graphics have to interface through generic drivers first, which isn't exactly the most optimal way to communicate with hardware, but it saves the developer from having to design 20 different copies of a game for every chipset out there.
tl;dr You can't compare the two the way you just did.