these are "Lyra Rays" and "Trixieshy" aka "Holly Blue", they're Taobao oddball/hybrid/factory second ponies made up from the wedding set (there was also a Pinkie Pie/Cherry Berry mashup but that one seems to be rarer). I believe these were ponies that were put together by factory workers specifically to sell on Taobao and similar sites (there were way too many of these two popping up for me to believe they were entirely accidental :p).
UK Ponycon ordered a bunch of the Trixies and used her as their con exclusive for one year (I can't remember the year off-hand, I'd check but I'm rushing atm), they dubbed her "Holly Blue" which is a type of butterfly
Some vendors at the con also sold their own stock of her (and Lyra Rays) that they'd ordered from Taobao themselves.
Never heard the name "Stella Bella" for Lyra Rays or seen her used as a con exclusive so can't comment on that
Not sure about price/value since the prices for the Taobao hybrids seems to have gone bonkers in the last few years