You have to look at it by cost per calorie, not necessarily cost per weight. I would bet that rice at $4.62 is more calories and carbs per $ than the oats and pasta. Some quick googling tells me this is the case.

I think sushi rice tastes better and is easier to eat than regular jasmine rice. I think rice is the easiest option since it's cheap, goes with anything, and digests well. Eating lots of oats is a chore and pasta usually takes longer to digest. But at the end of the day it's personal preference. This is the one I buy. Lasts a little over a month (and I eat A LOT of rice). https://www.amazon.com/Nishiki-Premium-Medium-Grain-15-Pound/dp/B004NRLAVY/ref=sr_1_2?dchild=1&keywords=sushi+rice+15+lb&qid=1614629699&sr=8-2

https://www.amazon.com/gp/product/B004NRLAVY/ref=oh_aui_detailpage_o08_s00?ie=UTF8&th=1

Literally the base of every single meal I eat. Add canned chicken, Rotel, and Valentina hot sauce and you have a Mexican meal. Do tuna, kimchi, and sriracha and you have a Southeast Asian meal.

Both options are a million times better if you already have a spice stash handy. If not, you can buy those premade seasoning packets on Amazon in something like taco or chow mein flavor or something.