"BTCST has undergone a 1:10 token redenomination on March 15th 2021 following the STP-4 Proposal. For more information: please refer to https://btcst.medium.com/btcst-to-implement-results-of-stp-4-1-10-redenomination-the-week-of-march-15-872c9ea3d5b7"
https://coinmarketcap.com/currencies/btc-standard-hashrate-token/markets/

So its possible that one exchange already switched to new tokens at a rate 1:10. So the spread is 8.9$ to 12$ not 89 cents to 12$. So much lower but still a lot which can be caused by locked withdrawals on one of exchanges.