There is a huge amount of friction. It's not clear whether they run market-maker operations to pick up the spread between Tether and $1. As always, the question is what actual assets Tether has to meet its claims.
Alameda Research (re: FTX exchange) normally makes a ton of money doing the arbitrage between dollars and tether but its having liquidity problems, so not doing it currently.
There is a huge amount of friction. It's not clear whether they run market-maker operations to pick up the spread between Tether and $1. As always, the question is what actual assets Tether has to meet its claims.