Any peg costs money. The cost = exactly that of a Long Straddle (buy one call at the money + buy one put at the money). Since STEEM is extremely volatile relative to most securities... a STEEM peg should be very expensive to maintain.

By employing unusual back-of-the-envelope methods to maintain a peg, you get the wild $0.80 to $1.40 range that we've seen in the last 2 months.