Some fantastic recon work was done by our friend over at Pick Me Up Some Mets. She actually took photos of various concession stand menus at the new Citi Field so you can see how much you're going to be expected to pay for a hot dog ($5.75 in case you're wondering).
The good news is the food options look really good. The prices are pricey, but not totally extravagant from what you'd expect. $17 for a lobster roll might be a little excessive.
Definitely check out the post over at Pick Me Up Some Mets.