A quote is the least informative document an agency will send you. Two firms can price the same brief 40% apart and both be right, because they have read different scopes into the same paragraph. What tells you more is how they behave before there is a contract.

Ask to see a portfolio in your problem space rather than your industry. A team that has shipped real-time tracking will handle your logistics product better than one that has done six logistics marketing sites. Then ask who specifically will work on it, and whether those people are the ones in the meeting.

Ownership and security are worth settling in writing, early. Who holds the repository, the app store accounts, the cloud project and the domain? What happens to them if the relationship ends? These are dull questions that become expensive ones later.

Finally, ask what happens after launch. An agency that treats support as an afterthought will hand you a product that works on the day it ships and degrades from there. The teams worth hiring plan for the year after release, not the week of it.