The only other way to get money in the Pokemon games outside of defeating Trainers in Pokemon Battles is by selling items.
By battling, of course.
Sell find items, in the description it might say "can be sold for a high price"
Well, without a gameshark you could keep on re battling the Elite 4 or trainers.
by selling items or battling trainers
by selling items and battling trainers
it depends on who you are battling with
You just have to keep saving money up, and battling to get money - simple!
Simply defeat another trainer.
You get an amulet coin and keep battling the elite four
You spend it in PokeMarts and you get more by selling stuff or battling trainers.
use an amulet coin on a Pokemon in a trainer battles
I belive that you beat the game, so just keep battling them, to get more than 25,000 Pokemon Dollars.