Kizashi Club

Has anyone had to replace an oxygen sensor yet? I was looking at the prices of these from Denson bosch etc. And wow are they expensive....im used to getting them for my Hondas which off amazon cost me around maybe 30-50 dollars each not in the 100s.

Also does anyone know who the OEM brand is? I thought possibly ntk (ngk) since it's Japanese...but according to amazon who could be wrong it states bosch being the oem brand

Definitely not Bosch. Japanese cars use Japanese OEMs for things like spark plugs and O2 sensors. I'm quite sure it's either Denso or NTK. I've replaced sensors in other cars with both of these brands and they are solid products.
As for price, yes, they are expensive but O2 sensors aren't really a maintenance part. You usually have to replace them when they throw a check engine light caused by a sensor malfunction. O2 sensors also typically last at least 100,000 miles and it's the upstream sensor that typically needs replacement before the downstream sensor.
Another reason why O2 sensors, especially Japanese ones, are expensive is due to white collar crime. Seriously. NGK, Denso, Mitsubishi, and a few others were busted for price fixing recently. Given they sell cars in the US, the US Department of Justice went after them in addition to Japanese authorities. I know of some American attorneys who have gone to Nagoya, Japan representing Denso against the US government.

Factory oxygen sensors are made in Japan so it's definitely not Bosch. As Kuro said, it's either Denso or NTK/NGK. Our factory plugs are NGK so maybe the oxygen sensors are from them as well?