Found 3 биржи where Prom is traded for BTC. According to the data on 28 September the most optimal price to exchange PROM for BTC is ₿0 for 1 Prom. This rate is fixed at BABYLONG at the maximum trading volume of the pair PROM/BTC - 0.1 BTC.
The maximum daily trading volume is observed in the PROM/USDT trading pair at Open Meta City and reaches ₿ 6.4 (1,444.14% of the exchange's total trading volumes) at the price ₿ 0 per 1 PROM.
The minimum price to buy PROM for BTC is 0 - on the exchange BABYLONG.