Unfortunately your probably right there. It wouldn't be so bad if I could just get 5 rounds of a few expensive loads to test instead of spending a ton on a full box just to test.
OP, Premium commercial cartridges usually have the type of bullet listed on the box.
Sadly, the person at the big box store or gun shop has no idea what those bullets will do.
This means you will have to do some due diligence on line and check out the bullets loaded into the ammunition you prefer is loaded with.
This can be a problem, because often commercial ammunition will have whichever appropriate bullet/powder/cartridge/primer combination that they found at the cheapest rate assembled into the cartridges at the time. This can and does change from lot to lot.
Obviously your funds are severely limited, from your post. I cringe when I read such stories stating "I only want to purchase five or ten cartridges at a time"
Still I've been in a position to know what it's like trying to scrape together enough money to purchase a box of cartridges.
At one point, I can remember a good friend of mine and I purchased a box of ammunition for our sportered 303 Brit rifles together and split it up between us. One mag full each.
We each took two shots at a homemade cardboard target at a paced 100 yards and when the rifles put both shots into the 10 inch (20cm) square, all was good to go. In those days, shots were seldom that far out.
In your case, at 200yds, even at the WSM velocities, which aren't extreme, the bullets should have performed well.
Did your bullet hit bone?? Sometimes that will flatten them out.
Cheaper cartridges tend not to list the type or quality of the bullet on their boxes or on their sites.
The only way to positively know what's in your cartridges is if you assemble the components yourself and I do realize this isn't always possible or affordable.
You might be able to find someone in your immediate area that will handload with better components for you, which will likely be cheaper than purchasing commercial cartridges.
If you're lucky enough to have a rifle that isn't fussy about what it shoots, bonus.