Very rough planning ranges for the local market, not contractor quotes, are:
Pressure-treated wood deck: $25–$45/sq. ft.
Typical planning allowance for a professionally built deck; elevation and railings can increase the price.
Composite deck: $40–$75+/sq. ft.
Higher initial cost, often lower ongoing surface maintenance than wood.
For a 300-square-foot area, those ranges suggest approximately:
Actual bids can differ considerably, especially if excavation, stairs, guardrails, retaining walls, difficult access, or drainage improvements are needed.
For comparison, a basic ground-level concrete patio with broom-finished concrete, assuming ordinary access and site conditions, will be about $10–$20/sq. ft.