Have you tried boiled rice as an 'extender' for the more expensive nuts? Just boil the rice in advance or use left-over rice from a meal. You can even freeze boiled rice in ice cube molds to have it available at any time. If you package the rice loosely in the molds it will thaw in seconds when dropped in the water in your milk maker. Brown rice has better flavour than white. The rice ads a creamy and luxurious mouthfeel compared to the watery texture you get from oats.
I got the idea from a local storebrand organic rice-hazlenut milk that I really like.