Strange POV IMO.
The non-canon Valks as well as recent canon Valks such as the Angel Birds have been selling pretty well. Certanly there's not huge piles sitting unsold in warehouses.
Yamato didn't really blow a whole load of money to produce them as the cost of the molds (the main expense) was paid for a long time ago. So it's only production and materials cost, plus a small amount of cost involved in development for choosing the paint and plastic colors to use. There is definitely profit being made on them. The more profit Yamato makes, the more it will encourage them to produce other Macross toys, such as those from Plus, Zero and others .
Graham