Low bids are usually built on something missing.
When one bid comes in significantly below the others, there's a reason. Sometimes it's a contractor who made an honest mistake in their takeoff. Sometimes it's a contractor who intentionally underprices to win work, knowing they'll recover margin through change orders once they're under contract. Sometimes it's a contractor who cuts corners on subcontractor quality, supervision, or site management to hit a number. In any of these cases, the owner absorbs the consequences.

A competitive market with qualified bidders tends to produce proposals within a reasonable range of each other. When one number sits well outside that range, the right question isn't how to take advantage of it. It's what that contractor knows, or is planning, that the others don't.

Change orders are where low bids become expensive projects.
A contractor who buys a job with a low number has to make their margin somewhere. The most common place is change orders. Scope gaps, ambiguous drawing details, site conditions, and owner requests all become opportunities to recover what wasn't priced into the original contract. An experienced contractor who bid the job honestly will handle these fairly. A contractor who needed to win at any cost will price them accordingly.

The owner who chose the low bid often finds themselves in a difficult position when this happens. They're already under contract, construction is underway, and their leverage is gone. Saying no to a change order can mean a work stoppage. The low bid that looked like savings on day one has become a negotiation they're losing on every line item.

Schedule failures cost money too.
A contractor who is underresourced, managing too many jobs, or relying on low-cost subcontractors will lose time on your project. That lost time has real costs: extended financing, delayed occupancy, consultants and staff carrying a project longer than planned, and in some cases, contractual penalties. These costs don't show up in the original bid comparison. They show up later, when the budget has already been set and the options for managing them are limited.

The right question isn't who is cheapest. It's who is most credible.
When you're evaluating bids, the number matters, but so does what's behind it. A thorough bid from a qualified contractor shows you what they're including, how they've handled contingency, and where they see risk in the project. It reflects how they think. A low bid from a contractor who can't explain their number in detail, hasn't identified the right risks, or can't show you relevant completed work is a proposal built on optimism, not experience.

The contractors who have been doing this long enough have watched the pattern play out too many times to count. They've walked onto jobs mid-construction where a low bidder walked off. They've been asked to price completion work on projects that went sideways. They know what a project looks like when the wrong contractor got the job, and it's never pretty for the owner.

Price matters. It would be dishonest to pretend otherwise. But price is one input in a decision that should also weigh experience, track record, financial stability, team quality, and the credibility of the number being put in front of you.