Cue cost has little to do with how much you'll like or dislike a cue.
Certainly having a $1000 cue might initially provide you with a sense of confidence but if the hit is too far off what you're used to that feeling will go away pretty quickly. I've spent ridiculous sums on cues and I've never found the price to do anything other than provide a feeling of confidence that you've bought a good cue. Let's face it, just because you don't play well with this cue doesn't mean some else won't. It's still a good cue, just not to your liking.
Hendry is a classic example of how a cue doesn't need to be expensive to allow one to play well, he won the vast majority of his titles using a cue that cost 40 pounds.
This is a little simplistic but I'd break players down into two different kinds of players, those who play by feel and those who play by pace or technique. Perhaps not the best description but it's the best I can come up with to describe how cue selections affect each type.
Feel players need to feel the impact of the tip on the cue ball to know how they've struck a ball. They "feel" the pace/delivery of the cue. If the feel goes off, shots get over hit, under hit, you name it.
Pace/technique players are a more robotic type player where the feel of the impact isn't so important as knowing they've delivered their stroke properly.
In short, feel players are playing by touch and pace players are playing almost purely technique. Most pros are a combination of both but they will lean towards one group or another naturally.
If you're a player that gauges shots based on the speed you deliver the cue (pace player) you can switch from cue to cue with less difficulty than if you're a player who plays by touch. I'm a "feel" player so while I might hit a shot with the same force, deliver the stroke to the same way and have similar backswing/follow through as someone who's not a "feel" player, I need to "feel" the impact a certain way to be confident I've hit the shot right. The feel of the shot more than the technique tells me if I've done it right.
When feel players loose their touch their games go out the window so obviously you need technique to fall back on on the days your touch isn't there. Pace players will tend to be more consistent because they don't rely on feel to produce. As long as their technique remains solid a pace player can play well even when they don't feel like they're playing well.
Feel players have to be much more selective in choosing their cues, specs alone does not make a good cue for a feel player. If you're a feel player you need to hit balls with prospective cues before buying, the feel of the cue is all important, even more than specs.
If you've bought a nice cue that meets all your specs but you're not playing well with it you need to figure out why.
If you're a feel player you might need lots of practice to adjust to the new feel of the cue. If it's too far off what you're used to, the time it takes to adjust to the cue might be quite a while and not worth the effort. As a feel player myself I'm not about to take 6 months to get used to a new feel, I'm going to look for something closer to what I'm used to.
If you're a pace player it's about making alignment adjustments to compensate for different throws from cue to cue.
If I were to decide on one all important factor in choosing a cue it would be the throw. IMO, nothing in the game is harder than knowing how to compensate for the throw of a cue. Trying to adjust this is the hardest part of using a new cue for both feel and technique players so if I had to pick one quality that I look for in every cue it's a similar throw to what I'm used to.
IMO, regardless of what type of player you are, as long as you find a cue with a familiar throw you'll be able to make the change with as little impact to your game/confidence as possible.
Things that will affect the throw are what should be your primary concern when choosing a new cue.
Wood: Ash or maple, maple throws very differently from ash.
Ferrule: Brass or fiber, each have very different throws
Certainly there are other specs that will affect throw but those above are IMO the most important ones.
Boy I hope with all that rambling I actually made some sense