Price Comparison for Concert Posters

I need someone to research and compare prices for concert posters, art prints and music memorabilia. This will help me understand the market value of my items.

The items to be compared are concert posters, art prints and music memorabilia

The price comparison should be sourced from:
- E-commerce websites
- Online auction sites
- eBay
- Etsy
The price comparison should be updated semi-annually.

Ideal skills and experience:
- Experience with online research
- Familiarity with e-commerce and auction platforms
- Attention to detail