What are some plants I could grow in my backyard for maximum profit?
It depends on where you live (your Plant Hardiness Zone) so that you actually have the climate for the plant. For instance, Saffron  is very expensive, so I’d think it would be a great crop for maximum profit .
It’s also cold hardy but you need to find saffron bulbs (not any crocus will do). It’s the most valuable spice on earth but costs a bit upfront.
Asparagus  is another expensive crop because it takes a couple of years to mature. A few years ago, 97% of asparagus was being imported into the US from Peru.
You can grow these in cold climates, but you need a bit more room than say a square foot of saffron.
Bamboo  appears to be another hot commodity. Last year, landscapers & homeowners in the US were paying as much as $150 for a potted variety. You’d probably need a greenhouse, though.
How much maximum profit I can earn?
Wild ginseng roots  command $500–600 per pound vs about $50 for cultivated roots. For sure for maximum profit.
Your Russian garlic  seems to sell (if you can find them) at about the same price as saffron bulbs.
They seem to grow in similar conditions as well, including colder climates.
I’d dare to think you’d have a readier market among home cooks, but then that leads to the next point: research your market first.
The product you decide to plant for profit really depends on who you will sell it to.
If you’re planning to sell the produce at the local farmers market (direct to home cooks), you’ll probably want to target buyers with something they actually use or would like in their homes.
If you plan to sell to a local grocer, you need to find out what’s in demand.
Personally, if I could figure out how to grow it, I’d opt for white truffles!