Black & white v. color

Good question actually. The most notable I can think of I think did it for stylistic purposes. Like Sin City: A Dame to Kill For, The Artist, Nebraska.

All commonly used cameras are only color. The "indy film" is the new Black & White.

There are some recent movies presented in B&W for artistic reasons but in some cases they are actually filmed in color and just converted/filtered to be presented in B&W.  As for when the last time B&W was chosen for cost reasons, this would depend on several factors, including what film stock was available in the respective country and what was available to the photographers.  As for the last time any major tv or film studio filming in B&W due to cost, my guess would be sometime in the early to mid 1970's.

For the broader question, when was the last ANY tv show or movie was produced in B&W because of cost savings, I found this on wikipedia regarding 1994's 'Clerks':

"In the case of Clerks, because of the extremely low budget, the production team could not afford the added costs of shooting in color. Although the difference in film stock price would have been slight, the store's fluorescent lights could not have been used to light for color. By shooting in black-and-white, the filmmakers did not have to rent lighting equipment."

That is the latest that I have ever heard of anyone choosing B&W over color due to cost, but it wasn't a major studio and was due to a unique reason, so I imagine there could be other cases since then.

For a more precise and objective answer, you could try and determine at what point color film became cheaper than B&W (or achieve relative parity) and look at what films/tv shows were produced around that time.

Manowar2010

I know the TV series DARK SHADOWS (the original one) went back and forth, sometimes in the same episode, due to cost. When I originally watched it, I never noticed. Years later, they were having a marathon on some local cable channel and I was at a hotel in a town that rolled up the streets at 7:30, so I stayed up all night watching. I was amazed how often there would be black and white as Caroline was talking to someone in one scene, then Barnabas would be in color during the next scene, then he'd be in black'n'white again while talking to the little nephew.

Usually though, I'd have to agree with the other posters- it seems like it is used for style (like the first few minutes of THE FALL (2006), or the whole YOUNG FRANKENSTEIN movie) rather than as a cost-cutting measure. I always liked watching black and white movies, and sometimes have skipped out on buying DVD/digital copies because they've been colorized. There's just a charm about the older black and white films that you lose when you colorize them (even with the newer, more accurate, and prettier way they are doing it where Errol Flynn doesn't have more rouge than Miss Piggy).

Following (1998) by Christopher Nolan
Made on a $6,000 budget, arguably used B&W for financial reasons.

These days it's the cheapest to shot on digital, no reason to use B&W to save money.