How much should Wayfair pay for reviews to increase sales?

We have 100 products without any reviews today. Our analysis shows that on average having 5 reviews can have a positive impact on sales/order. We are considering paying for reviews in order to increase sales. How much do you think we should pay for each review? Average price of products: $200. Average gross margin: 20%. Monthly conversion rate is expected to increase from 2% to 3% with paid reviews. We want to ideally break even in 6 months' time.