Great question...
I think that you can get a cue that will play up to your ability, even if you are SVB or Efren, for under $1500, maybe even below $1000.
Why then would you want to bring a $1500+ cue out to poolrooms and maybe even bars to play? Four reasons come to my mind:
1. You want to show off your high end equipment. I may fall into this category as I am a self-admitted showoff. I have a smallish (less than 30) cue collection in which there are a strong number of upper end sticks and I have been known to bring some out to play. After an unfortunate ding or two, however, I have ratcheted down my enthusiasm for showing off, giving way to better sense, and now almost exclusively I use either my $800 Olney or $800 Scruggs.
2. The magic wand. After searching and trying so many cues you feel that you found the best hitter of all time; it's your sweet hitting monster player and even though it cost mucho denero, you're using it.
3. Your flush with money, or at least comfortable enough financially, that taking and using very a high-dollar cue out to play isn't going to have that much of an effect on you, even if it gets dinged up a little.
4. There are those who feel that cues were made to be played and should not be display-rack-queens regardless of cost. There have been a number of posters already in this thread alluding to having this mindset. I salute those of you who feel this way. Despite my generally being a bit of a showoff, I don't believe I could take, for instance, Kikel's "Pink Dianthus" over to Sully's Cafe for the Friday night 8-ball tourney.

I would be way too on edge like I left a 2010 Lamborghini parked over at the Stop & Shop parking lot.
I voted for 'less than $2000' but if there was a 'less than $1500' option I would have clicked on that one.
Best,
Brian kc