Actually; 38spl can be bought VERY CHEAP. The problem is, people's eyes aren't focused.
The average price for a box of 38spl rounds is $14-$15. That's single box and/or bulk. Where your eyes mislead you is that there are 50 rounds in a box of pistol ammo. (Not home defense rounds). That comes out to $0.28-$0.30 per round. OR, in rifle terms, $5.60 - $6.00 for a box of 20. HELLO!!! Brass case .223 isn't even that cheap normally, and that's about the cheapest rifle ammo you're going to find.
30-30 ammo is 3X as much as 38spl ammo. And if you started reloading, you could drop the price in half. Don't let your eyes deceive you. The 38spl is cheaper to shoot than the 30-30 or most other rounds. (Even some russian like 7.62x54, unless you buy bulk mil-surplus).
Also; don't let other's personal opinion that "Rifle rounds are for rifles,,,, and pistol rounds are for pistols". That's personal ignorance. Yes, the cowboys and such had the same caliber for pistol and rifle because they loaded their own, and it's easier to carry the makings for one caliber instead of two. But let's be real. The 357 magnum didn't even come about until the 20th century. The single caliber back then was the 45LC and others. That doesn't mean the 357 mag can't be a good carbine round. It definitely can be. Great for home defense. Good for deer out to 100 yards. Good on coyotes, varmints, etc...
Let's be realistic here. The M-16/AR-15 .223/5.56 was DESIGNED for one and one reason only. Shooting people at close ranges. "Under 100 yards". Well, that has developed into the M4 and has been modified in every direction. The military still considers the .223/5.56 as a close quarters battle caliber. But there are a lot of AR15 lovers; many who are also in the gun business and competition world; who are convinced that the AR specs make is a great 500-600 yard gun. Well, the specs on my car says it can go 150mph, but that doesn't mean it was built or designed to go that fast. Same with the 357 magnum. The round indeed, along with the 38spl, was designed for defensive purposes out of a pistol. But as it evolved, and people realized that the bullet weight was about the same weight as many rifles, 150-180 grain, they figured they could pump up the powder and make it a multi-purpose round.
Anyway; there isn't a damn thing wrong with using the 357/38spl in a rifle. It's great for plinking 38spl to around 50 yards. Good for deer with the 357 out to 100 yards. And 38spl is fairly inexpensive to shoot. Just don't let your eyes become deceived. A box of 20 38spls costs LESS than a box of 20 .223. And 1/3 the cost of 30-30.