The helicopter world has a minimum of 400 hours in a helicopter before being eligible to even hold an instructor rating. The aeroplane world needs some similar restriction as well, to be a disincentive for instructors who are only there to "hour build".
Without this there would be a shortage of aeroplane instructors and reduced flow on into higher licensed instructing positions.
Many of the schools earn their bread and butter from the student to CPL to instructor to employee cycle. The ones that survive and end up grade 1s keep slogging it out as it would be a pay cut to head north and try their luck at charter.
I'm not saying this system is a good thing, quite the contrary. However it is required to keep instructors in the system.
Do you think someone who has got a 1000 plus hours up north, probably flying a twin or looking at a CIR would come back and fork out the money for an instructor rating and start off on reduced pay as a casual grade 3? I can say after flying Airvans, 210s, Barons, Navajos, Chieftains, Partenavias, 402/404s I wasn't overly enthused about watching a foreign national fly a Cessna 152
Dreaming