Outside of BA, IB and AA, discount economy earns 25% accross the board. It's up to LAN how much they feel they can charge for discount economy tickets, not BA.
How much is the full flex economy? Or business?

That said there are additional restrictions on LAN discount economy fares which are not so common, most discount classes have the following restrictions:

1 Not eligible for Accrual of Avios on Flights that operate wholly within Peru.
2 Not eligible for Accrual of Avios on Flights that operate wholly within Chile.
3 Not eligible for Accrual of Avios on Flights that operate wholly within Argentina.
4 Not eligible for Accrual of Avios on Flights that operate wholly within Ecuador.
5 Available on certain flights within South America.

I wonder if this is a BA restriction, or LAN not wanting to pay BA for Avios earnt on these routes?