In light of a recent change with chain-selling artifacts to a shopkeeper (can't find the rfe though :/), I'll post you this:
You examine Waldenbrook. Diagnosis: Level: 12, DV: 23, PV: 10, Hits: 421,
Attacks: 3, Damage: 21-36. Speed: 151.
How many do you want to drop (ENTER = 4)?
Waldenbrook mumbles: "I'd offer 341 gold pieces for yer uncursed si." Do you
want to accept the offer? [Y/n]
You drop the uncursed si. Waldenbrook seems to grow in confidence! And
power...
Which direction [789456123, Z = ABORT]?
You examine Waldenbrook. Diagnosis: Level: 17, DV: 26, PV: 11, Hits: 435,
Attacks: 3, Damage: 22-37. Speed: 151.
I think it seriously lacks speed. RFE for +1 speed per monster level?
Also HP gains are disproportionately small - just 3 hp per level? It should be atleast 2% of base HP (no less then 1) + 3 hp per level!
Then it will be nice and balanced and quite mightly shopkeeper of UlTiMaTe ChAoS!
I was just going to mention this as I experienced the same thing last night - Sold a few stacks of si to the Black Market and repeatedly got the message that shopkeeper looks stronger. Haven't tried selling them any major artifacts, but maybe the Si only adds a minor increase while others add more?
You get the same message, probably just a straight increase per artifact sale. I got a little worried Abbott the message the first time I saw it, until I remembered the RFE