I don't care if it's dual, single, or triple GPU on a single card, if it performs it performs and you can compare it on a price level/power/performance level then.
And to add there is still a sizable market for dual GPU on single card and specifically the more lucrative HPC segment; Nvidia still sells its venerable dual GPU K80 that seems to have a reasonable market due to its FP64 and price (AMD also has a product that competes well in this regard for price and performance).
So like you say performance and price within acceptable power envelope that is usually 300W.
Cheers