Nepenthes ephippiata is a species closely allied with N. lowii. This species doesn't have the dramatic pinched in waist as N. lowii has from what I've read. It does have the hairy underlid that N. lowii has. Overall this species is similar in cultivation and growing conditions as N. lowii. It does well outdoors and can take a lot of light. I've had no problems with this species. It is a bit of a slow grower but perhaps slightly more vigorous than N. lowii. It's a very nice species that tends to get overshadowed by its more spectacular counterpart N. lowii. 

Cultivation: easy; rather slow growing, similar care to growing N. lowii
Market availability: size 2 to size 3; fairly common
Species variability: none that I'm aware of
$ / size: moderate-$30.00 and up
Cuttings: none available for trade
Sex: unknown