Agreed it sounds expensive. At least in the UK, there are loads of ex-crypto-mining RX580 cards floating around for about the same money, and probably twice the performance (for DT in OpenCL). Quite power-hungry though.
Also, iirc, the Nvidia1050 was a bit disappointing compared to the 1060 (which shouldn’t be all that more expensive and seems to perform a lot better with darktable)
Thanks to everybody. @Claes@benp Indeed I’ve found it new at 140€, and this page on Phoronix confirms @rvietor remarks.
I think I’ll lump more money for a better card.