It's actually the exact opposite...350 Legend is some of the most affordable centerfire rifle ammo available...and the nice thing is: it is AVAILABLE!! EVERYWHERE! Maybe his is 450 Bushmaster??? That stuff is like $40-45/box...
I have two of these gems...an 18" AR-15 Upper and a Savage Axis XP 16" Heavy Barrel. No recoil, accurate (sub-MOA with both rifles at 100 yards), inexpensive ammo to include FMJ plinking ammo @ $15/box, great terminal performance...what's not to like? My niece and nephew have killed a couple deer this year with their 350 Legend. Great on-game performance! None of the deer went over 60 yards and had good blood trails that a 9 and 11 year old could follow. For my AR upper I have two 10-round P-Mags that I modified from 5.56 to 350 Legend with a Dremel tool and a sanding drum. They work flawlessly and having 10 rounds of .35 caliber ammo in a handy, quick-pointing rifle is awesome! I am contemplating taking the 3-9x40 scope off my AR and mounting a red dot and using it for deer drives.
The ammo, like all ammo, went up a LOT this year. When I purchased my upper two years ago, Deer Season XP 150 gr. ammo was $19.94/box at WalMart and 145 gr. FMJ was $9.96/box. Now the Deer Season XP is $32-34/box and the FMJ are $15/box.
But to answer your question...GET ONE! It is a very fun caliber to shoot and works very well on deer out to 200 yards. I bought a set of reloading dies and am starting to roll my own ammo for mine as well...which is almost as fun as shooting my 350's!