Welcome to the world of rangefinders.
I've had several, and yes its been my experience that most will reliably read half what is advertised.
I say reliably, I mean something you can depend on, and it will also depend on where you are.
I have a Leopold RXIII, its advertised to be good for 1200 yards on reflective targets and 600 on deer.
I've never got to 1200 yards, or rare occasions I've gotten 800+ in the mountains but in the prairie I'd be real lucky to get to 300 on antelope.
There are really good Range finders out there that will range much farther then you can shoot.
The Terrapin is a good one, but they are discontinued. I was at a precision rifle match and we were talking about range finders and I played with a Terrapin. Its suppose to be good for 2000 yards. I was able to get 3300 on a couple reading, it was really good for 2000 as advertised. That was the one I wanted.
UNTIL:
I was on a guided hunt and we were talking range finders and I related that I was going to buy a Terrapin, but since they are discontinued I was searching for a good used on. The guide told me to try a G7 from Gunwoks first. He dug his out and I was impressed. Its suppose to be good to 2000 and using the Guides, I didn't find anything that far but I found it would range much farther then I'd want to hunt with. Plus it has a ballistic program built in.
So when I get home I ordered on. It took it out the first afternoon and ranged a cow, (convectively) at 2280. I've ranged several animals beyond 2000 so it works.
Now the Ballistic program: Its only good for 1400, meaning, like any other ballistic program, you put in you bullet data, BC, velocity, etc. and it gives you corrections. It computes the temp, alt. humidity, angles, etc and gives you the correction in MOA for the range. Like I said the Ballistic program is only good to 1400, past that you have to use your data book.
You can put several ammo combinations and then just select the load and go.
The price is reasonable for the price ($1600).
The G7 isn't the only one out there that works, its the one I tried, liked and bought. Well worth the money spent.
In short there are a lot of good range finders out there, but you're going to have to pay for them The Terrapin I mentioned was $2000 new.
Might want to look at the Vortex models, I don't now anything about them but lately I've been trying other Vortex optics and found them to be excellent quality and exceptional warrantees.
If youre into long range shooting a quality range finder is a must. If you only hunt to 300 or so yards the others, like the Leopold will work.
I just don't seem the logic of spending tons of money on long range rifles and skimp on the range finder.......the weakest link limits your shooting. My confidence is better if I know Im the weakest link and not the equipment.