modbender Price Tracker
Overview
Track product prices across multiple e-commerce platforms to identify arbitrage opportunities, profit margins, and optimal buying/selling windows. This skill enables automated price monitoring, historical tracking, and revenue-focused decision making.
Core Capabilities
1. Product Discovery & Monitoring
Search and Track Products:
- Search products by keyword across Amazon, eBay, Walmart, Best Buy
- Add products to monitoring lists
- Set target price thresholds
- Configure alert frequency (hourly, daily, weekly)
Example Request: "Monitor iPhone 15 Pro prices across Amazon and eBay. Alert me if the price drops below $800 or if eBay listing is $150+ cheaper than Amazon."
2. Arbitrage Analysis
Cross-Platform Comparison:
- Compare identical product prices across platforms
- Calculate profit margins after fees and shipping
- Identify flip-worthy opportunities (20%+ margin after costs)
- Factor in platform fees, shipping costs, and taxes
Fee Structure Reference:
- Amazon: ~15% referral fee
- eBay: ~13% final value fee + listing fees
- Walmart: ~8-15% referral fee
Example Request: "Find Nintendo Switch bundles where eBay price is 20%+ higher than Amazon, accounting for all fees and shipping costs."
3. Historical Price Tracking
Price History:
- Track price changes over time (30, 60, 90 days)
- Identify seasonal pricing patterns
- Detect price manipulation or flash sales
- Export historical data for analysis
Example Request: "Show me the price history for AirPods Pro 2 over the last 60 days. Identify the best buying window."
4. Automated Alerts
Alert Configuration:
- Price drop alerts (below threshold)
- Arbitrage opportunity alerts (margin threshold)
- Competitor price alerts (when competitor lowers price)
- Bulk product monitoring
Example Request: "Set up alerts for all Sony TV models. Alert me if any model drops below $400 or has 25%+ arbitrage margin."
Quick Start
Track a Single Product
# Use scripts/track_product.py
python3 scripts/track_product.py \
--product "Apple iPhone 15 Pro 256GB" \
--platforms amazon,ebay \
--alert-below 800 \
--alert-margin 0.20
Bulk Monitor Products from CSV
# Use scripts/bulk_monitor.py
python3 scripts/bulk_monitor.py \
--csv products.csv \
--margin-threshold 0.25 \
--alert-frequency daily
Price Comparison Report
# Use scripts/compare_prices.py
python3 scripts/compare_prices.py \
--keyword "Sony WH-1000XM5" \
--platforms amazon,ebay,walmart,bestbuy \
--report markdown
Workflow
Arbitrage Opportunity Discovery
- Search for products in high-demand categories (electronics, gaming, home goods)
- Compare prices across all platforms using
compare_prices.py - Calculate net profit after fees/shipping/taxes
- Filter opportunities with 20%+ margin
- Verify product condition and seller reliability
- Execute or set monitoring for price drops
Price Drop Monitoring
- Identify target products (wishlist, seasonally discounted items)
- Set alert thresholds using
track_product.py - Monitor historical patterns to predict optimal buy windows
- Act when price drops below threshold
- Repeat for seasonal shopping events (Prime Day, Black Friday)
Scripts
track_product.py
Track a single product across platforms with configurable alerts.
Parameters:
--product: Product name/keyword--platforms: Comma-separated platforms (amazon,ebay,walmart,bestbuy)--alert-below: Alert when price drops below this amount--alert-margin: Alert when arbitrage margin exceeds this fraction (e.g., 0.20 = 20%)--frequency: Check frequency (hourly,daily,weekly)--output: Output format (json,csv,markdown)
Example:
python3 scripts/track_product.py \
--product "Samsung Galaxy S24 Ultra 256GB" \
--platforms amazon,ebay,walmart \
--alert-below 900 \
--alert-margin 0.25 \
--frequency daily \
--output markdown
compare_prices.py
Compare prices for a product across all platforms.
Parameters:
--keyword: Product search keyword--platforms: Comma-separated platforms (default: all)--report: Report format (markdown,json,csv)--sort-by: Sort by price, margin, or rating--min-rating: Minimum seller rating
Example:
python3 scripts/compare_prices.py \
--keyword "PlayStation 5 Slim" \
--platforms amazon,ebay,walmart,bestbuy \
--report markdown \
--sort-by margin \
--min-rating 4.5
bulk_monitor.py
Monitor multiple products from a CSV file.
CSV Format:
product,platforms,alert_below,alert_margin
"Apple MacBook Air M3 256GB",amazon,ebay,walmart,899,0.20
"Sony PlayStation 5",amazon,ebay,399,0.25
"Dyson V15 Detect",amazon,walmart,bestbuy,500,0.18
Parameters:
--csv: Path to CSV file--margin-threshold: Minimum margin to report--alert-frequency: Frequency of alerts--output: Output file for alerts
Example:
python3 scripts/bulk_monitor.py \
--csv products.csv \
--margin-threshold 0.20 \
--alert-frequency daily \
--output alerts.txt
price_history.py
Retrieve and analyze historical price data.
Parameters:
--product: Product name/keyword--days: Number of days of history (default: 30)--platform: Specific platform (optional)--output: Output format (markdown,json,csv)--trend-analysis: Include trend analysis and predictions
Example:
python3 scripts/price_history.py \
--product "AirPods Pro 2" \
--days 60 \
--trend-analysis \
--output markdown
Best Practices
Arbitrage Profit Calculation
Always calculate net profit:
Net Profit = (Sell Price - Buy Price)
- Platform Fees
- Shipping Costs
- Payment Processing Fees
- Taxes
Recommended minimum margin: 20-25% to account for:
- Unexpected shipping delays
- Returns/refunds
- Market price fluctuations
- Time value of money
Risk Mitigation
- Verify seller reliability - Check ratings and reviews
- Check product condition - New, refurbished, or used
- Factor in return windows - Platforms have different policies
- Monitor price stability - Volatile prices increase risk
- Stay within limits - Don't over-leverage on single opportunities
Seasonal Patterns
- Q4 (Oct-Dec): Holiday sales, best for electronics
- January: Post-holiday clearance
- Prime Day (July): Amazon-specific deals
- Black Friday/Cyber Monday: Cross-platform discounts
- Back-to-School (Aug-Sep): Laptops, tablets, accessories
Automation Integration
Set Up Cron Jobs for Automated Monitoring
# Check prices every 6 hours
0 */6 * * * /path/to/price-tracker/scripts/bulk_monitor.py --csv products.csv --output alerts.txt
# Daily arbitrage scan
0 9 * * * /path/to/price-tracker/scripts/compare_prices.py --keyword "high-demand-products" --report markdown >> /path/to/reports.txt
Integration with Notifications
Combine with notification systems (email, Discord, Telegram) to receive real-time alerts when opportunities are detected.
Limitations
- Platform API rate limits may affect search frequency
- Real-time prices may have slight delays
- Some platforms restrict scraping (comply with ToS)
- Seller inventory changes rapidly
Revenue first. Track smart. Flip fast.