Can't get your point clearly but binance is trading platform so they don't take price from other bitcoin exchange platforms.

They have USDT-BTC pair where buyer/seller set orders to buy/sell bitcoin and bitcoin price there is in terms of USDT not interms of USD like in Gdax or coinbase.

USDT always tend to maintain 1:1 exchange rate with USD but sometime it might valued lower or higher than that.

IOTA-BTC pair might have moved up so you can't get equal amount of IOTA from those bitcoin you have got after selling IOTA in past.