They basically cost like $5000 usd each, and BTC was like $10, so people paid 500 BTC for the miner, then 2 years later they issued refunds in BTC but at the original USD cost, so people got back like 5 BTC instead of the 500 BTC that they paid.
However I am pretty sure if BTC went the other way and hit $1, they would send the original 500 BTC back instead of the actual USD value of 5000 BTC.
Black Arrow did something similar. I want to say around the same timeframe, 2013ish. I paid in BTC and got refunded USD after my cancelled pre-order. I def lost out there....