Gutters look like a small job until you price it by the house instead of by the foot. A typical single-story home might need 150 to 200 linear feet, and the material you pick swings the total more than almost anything else on the quote.
The decisions are simple once you separate them: material and gauge, seamless vs. sectional, how many downspouts the roof actually needs, and whether guards are worth adding now or later. Get a price per linear foot instead of one lump number, and a quote becomes easy to compare.
This page covers what gutter installation costs nationally, seamless vs. sectional, K-style vs. half-round, when fascia repair is really needed, guards, and what a fair written quote includes. City pages linked below carry local pricing and licensing for your market.