Some people actually do have that much tu.Also, those rare eggs are usually bought from the CS.
But they are probably retired CS eggs, which is why they're priced so high.
Or Kir eggs.
As for the beans, I think you're better off selling them.
But if you think you're lucky enough to bean your pet a high color, then go right ahead. o3o
People are getting their tu by multiple ways.
Most are getting them by playing the stocks.
Others are just selling rare eggs/items, high pet colors, CS/Kir pets, and rare names.
The fortunate few that are decent artists are getting their tu by doing commissions for others.