Key PointsEight of the top 10 most valuable firms lost Rs 1.55 lakh crore in market capitalization last week.HDFC Bank and Bajaj Finance were the biggest contributors to the market cap erosion.The overall market capitalization of BSE-listed firms fell by over Rs 20 lakh crore.Tata Consultancy Services (TCS) and Larsen & Toubro (L&T) were the only top firms to gain valuation.