Also, this may seem obvious, but don't accept the advice of any sales associate that doesn't look good. They're
at work, in the fashion industry, and if you don't think they're killin' it, you're "just looking around" until a better-dressed associate comes by. Make sure to get someone who cares.
Regarding price, I pay about $700-800 for made-to-measure suits from a private dealer (this is a lot less hoity-toity than it sounds; they're pretty common, cheap, handy small businesses). I could have six suits right now instead of my current three, but they wouldn't last as long, I'd feel underdressed or uncomfortable in worse fabric and a lousy cut, and I'd have to rotate the cheaper suits out when I was able to afford suits that make me look like a professional instead of someone's awkward prom date.
Everyone says your first suit is an investment in your career, but very few people seem to take them seriously, even though the word "vestment" is right in there! Every day that I'm in court, people seeking a lawyer come up to me and ask me questions. When I ask them how they picked me out, they all say the same thing: "you looked like a lawyer". (That is, unless they saw me cross the bar. For those folks, it's a dead giveaway.)
It's interesting to note in many cases that they didn't ask much more experienced (i.e., non-student) counsel that were hanging out near me. They make high-five, low-six figure salaries, and I owe about that much in student debt. And they're way, way more qualified and deserving of respect than I am. But apparently when someone's radar is up to find a lawyer, they gravitate towards the guy in a fitted suit, buffed oxfords and a pocket square. Not a bad image to project when you're applying for jobs. If you already
look like a lawyer, your interviewer starts from the mental position that you're essentially one of them that hasn't come out of school yet, instead of an aspiring student hoping to
become one of them.
Realistically, you're shopping for something you're going to have to wear twice a week for four months straight, perhaps in your first year, likely in your second, and again twice a week for the rest of your life once you start articling. You really don't want to spend 40% of your young working life looking rumpled and uncomfortable, having trouble lifting your arms and getting hot around the neck and armpits. It's totally worth the extra $200-$300 to make such a large portion of your life much more breathable and comfortable, and (most importantly) to give yourself the little bit of confidence that will come in handy when you feel more inept and incompetent than you have at any other time in your life.

So, uh, cheers!