Musical Instrument Site Price History Overlay

WHAT IT DOES

This script scans musical instrument product pages—Reverb, Guitar Center, Sweetwater, and others—for price data including current price, list price, sale price, and historical price mentions. It displays a floating overlay showing a price history chart with key metrics. The script extracts pricing information from the page, calculates discount percentages, and shows a summary of price trends. A chart displays price over time using sequential snapshots, highlights the lowest and highest prices, and shows a fair price estimate. A one-click export function saves price history data as CSV or JSON. All price snapshots are stored per domain locally for tracking over time.

WHERE IT RUNS

Works on any musical instrument product page—Reverb, Guitar Center, Sweetwater, Musician's Friend, or any page displaying product prices. The script detects pricing information using common patterns and selectors, making it compatible with most musical instrument retail sites.

HOW TO USE

The panel appears automatically when you visit a product page. It detects the current price, list price, and sale price, and displays them in a grid with color-coding: green for current price, gray for list price, blue for sale price. Product name, brand, model, and condition are shown when available. If a list price is higher than the current price, the discount percentage is calculated and displayed. The price history chart shows your saved snapshots—each visit saves a snapshot, building a history of price changes. The chart bars are color-coded: green for the lowest price, red for the highest, blue for others. Average, lowest, and highest prices are shown below the chart. Click "Refresh Data" to rescan for updated prices. Export price history as CSV for spreadsheet analysis or as JSON for programmatic use. Use "Clear History" to reset stored snapshots for the current domain. The panel automatically saves a snapshot each time you visit, building a history of price changes over time.

TECHNICAL MECHANISM: PRICE EXTRACTION WITH CURRENCY PARSING AND HISTORICAL CHARTING

The script uses a comprehensive detection strategy. First, it extracts the product name from h1 or title elements. Brand, model, and condition are extracted from patterns like "Brand: [Name]," "Model: [Name]," and "Condition: [Name]." Current price is extracted using patterns like "Price: $[amount]" and "Now: $[amount]." List price is extracted from patterns like "List: $[amount]" and "MSRP: $[amount]." Sale price is extracted from patterns like "Sale: $[amount]" and "Save $[amount]." The script also scans elements with price-related class names (.price, .product-price, .current-price, .sale-price, .price-amount) to find additional price values. Historical price mentions are extracted from patterns like "Was $[amount]" and "Price dropped from $[amount]." The currency parser handles $ symbols and commas, converting to numbers. The discount percentage is calculated as (list - current) / list × 100. The price chart displays the last 20 snapshots as a bar chart with color-coding based on whether the price is the lowest, highest, or other. Average, lowest, and highest prices are calculated from the snapshot data. Each snapshot stores the current price, list price, sale price, product name, brand, model, and condition with a timestamp, capped at 30 entries per domain.

THE PANEL

The price history overlay appears in a draggable, resizable panel that remembers its position per site. The panel shows product info, price cards, discount indicator, price chart with legend, price statistics, and history. Drag by the header to reposition, collapse to a compact icon with a click, and resize using the bottom-right corner. The panel snaps to screen edges for tidy placement and closes with the Escape key. All settings—panel position—persist per website using GM_setValue, so your view returns exactly as you left it.

PLEASE NOTE

This script requires the free BotGentz extension to run. The script relies on common product page structures—if a site uses a non-standard layout, price detection may be incomplete. The script does not access your retail account credentials—all data is read from the visible page and stored locally. The currency parser assumes USD formatting; other currencies may not parse correctly. The price chart uses snapshots saved on each page visit; visit the product page regularly to build a meaningful history. All data is stored locally in your browser via GM_setValue and never transmitted. The script is designed for tracking prices, not for modifying or uploading data to retail sites.