Let's do the math.
52 weeks/year and 40 hours/week = 2080 hours.
You can turn those knobs up/down based on vacation, non-billable time, etc, but just to pick a number, let's say you have 1,500 billed hours per year. $250,000 / 1,500 hours = $167/hour. I know car mechanics who make more than that.
If someone's telling you $250k isn't realistic, they're either underestimating hours worked, or underestimating billable rates, or thinking about being a full time employee of a consulting company (rather than an independent consultant.) They're likely contractors, not consultants.
And hey, why stop at $250k?