Shopaholic is an achievement in the Hearts of Stone expansion and is achieved by buying all three items during the auction portion of the main quest Open Sesame!.
To complete this, you must have at least 710 
(670 if you didn't tell Vimme Vivaldi about the painting):
- Count Romilly's figurine: 300
- "Starry Night Over the Pontar": 20 or 60
- The Professor's spectacles: 350