It depends on how easy they make it to hop between worlds. I'm 100% sure a certain amount of population (cheapskate virgos) will use it no matter what to the fullest extent even if it wasn't as good gil as actually farming the gil for the time spent. Then there are people like me who wont use it unless we want to play with a friend on the other world, ignoring mb there unless we actually need to buy something and then buy it whatever the price as long as it's not outrageously expensive.

Not everybody will care enough to realmhop for better deals when they know time is gil anyways, unless prices are so far apart. They probably make trip to the cheapest botty-server and buy a lot of stuff at once, if they're wise about it, so they dont have to do many realm-hops because that's a bother.

A lot of people buy gil even though it's not allowed so they can afford higher prices and be less bothered about it. I'm not sure markets will be fine, but it won't be a total collapse.