A job bid today may not start for many months. Supplier quotes expire. Wage agreements step up on set dates.
Example: a supplier holds a steel price for a short period. The project schedule shows steel delivery well after that. The bidder must cover the gap.
Check the schedule and the expected start date before you price. Ask suppliers how long they hold the quote. Check whether the contract has an escalation clause. If it has none, the risk is yours. Carry money for it or qualify your bid with a price-hold date.