There are various high voltage op-amps available.
True, but it's much better than other TI and AD/LTC HV devices wrt Ibias, voltage noise and CMRR (at least) specs. TI have a new 180V OPA462 with 2pA typical @ 25C compared to 300fA for the ADHV4702, 100pA max ct. 2pA and much higher noise. Maybe better parts are available elsewhere. I don't normally post about new product releases but this one caught my eye as the specs seemed particularly impressive.
They're not cheap. If you're doing a large volume it starts to make more sense to use a low voltage op-amp with a discrete high voltage gain stage.
Or bootstrap the supply voltage of a low voltage amp to that of the incoming signal. Either way, you may have to make other significant compromises such as additional, higher leakage input protection (not easy to match the amp's 2pA over temperature) or higher input offset drift TC.
HV applications isn't something I know much about, hence my question as to what applications might this amp be particulary suited that could justify the high cost? SMUs might be one?