The price of a new 320GB PS3 is the same as a Vita with a 16GB memory card, so you must have thought that the PS3 was a better investment. It's hard to argue with that. If I didn't have a PS3, I would buy one before buying a Vita. I don't expect a price decrease on new Vitas anytime soon. Sales of the console are slow, but Sony doesn't seem inclined to address that problem with a price decrease. It worked for Nintendo with the 3DS, but Nintendo had lots of profits from the DSi and DSI XL to offset any short term losses on the 3DS. The PSP's sales aren't high enough to do that. As with Sony's previous consoles, there is likely to be a revised design released at a lower price in 2013 or 2014. In the meantime, you can also find used Vitas for sale for significantly less than a new one.
You can always buy a used one. They're about $40 - $50 cheaper depending on where you get it from (If memory served correctly, you can buy a used wi-fi vita from gamestop for $209 and a 3G one for $249.) Sony has no plans on coming out with a newer model anytime soon (but I bet you they will) and they plan on lowering the price sometime next year.