If you look at normal lenses, then look at cinema lenses of comparable aperture and focal length, you might be shocked by their prices over their counterparts. This fun video examines just why cinema lenses are so expensive.
Coming to you from ZY Productions, this great video talks about why cinema lenses are so expensive. If you're used to standand lens prices, you might be thoroughly shocked if you've never seen how much an equivalent cinema lens costs. In case you're wondering what T-stops are, these are f-stops adjusted for light transmittance. No lens transmits 100% of the light that enters it, so while the f-stop of the lens may be accurate for describing depth of field parameters, it actually overestimates how much light is making it to the camera sensor. While this error might not matter much to a stills photographer, in film, even slight variances in exposure can be quite noticeable, so it's crucial that cinematographers be able to rely on getting the exact same exposures as they switch between lenses. In short, you can think of T-stops sort of as f-stops of light transmittance. Check out the video above for more on the topic.