Stack Calculator

What it does

Pillar #13 made executable. Enter a planned purchase (set + retailer + planned date). The calculator stacks every applicable margin lever: base discount, current GWP eligibility, LEGO Insiders points earned (at current 1x/2x/3x event rate), card cashback, and Target receipt-submission credit. Output: true cost basis, projected exit, and net ROI on that basis.

Why it matters

Most LEGO investors leave 10-25% of their potential ROI on the table by failing to stack. The calculator makes the stack visible, automatic, and shareable. Members go from 'I think I saved a few bucks' to 'my true cost basis was $245 on a $300 sticker — locking in 357% net ROI at target.'

Core features

• Multi-retailer stack templates (LEGO.com, Amazon, Target, Walmart)
• Real-time 2x VIP event detection from LEGO.com promo feed
• Card-cashback profile per member (which card, what %)
• GWP overlay: free set + projected resale value of GWP
• Target receipt submission reminder (within 24h discipline)
• Save calculations to Portfolio as planned acquisitions

Example flow

1. Member inputs: LEGO 10316 LOTR Rivendell at LEGO.com, weekend of 6/15
2. Calculator detects 2x VIP event for that weekend
3. Member's stored profile: 5% cashback card
4. Current GWP: Polybag set worth $25 resale at $200 spend threshold
5. Output: Sticker $499 → True basis ~$425 → Target exit $1,488 → Net ROI 250%

Wireframe