As someone who is entering school in the fall, I've been starting to purchase items that I'll need, such as steths and cuffs, and I've done some research and asked around to nursing friends.
The result I came up with is this: Buy a lower-quality scope, maybe a $30-40 one. This scope will be the one you keep in your car's trunk just in case you forget your normal one, so you don't have to go back home to get it.
Buy a higher-quality one, $70-100. This will be the one that you'll learn the most with, get the most hands-on practice with in clinicals and labs; but it's also not a huge loss if someone walks away with it, and it's easily replaceable.
When you graduate, or even start your 2nd year, invest in a high-quality Cardiac 3 or equivalent - the $140+ ones. By this time, you'll be comfortable and familiar, and you'll be used to keeping hold of your scope so nobody runs off with it. I plan on buying this as a kind of reward for beginning my 2nd year. Until then, my $80 Clinical I scope will do juuuust fine.
I do recommend buying a single-tube and a dual-tube, and learning how to effectively use both - I've heard many people state that dual tube scopes are harder to use, but I prefer the dual I got to my single Clinical I so far.... that might just be because I was told to get a single-tube, and I always like going against the grain