A casual task asks for a fixed delivery or a number of kills and pays fixed resources, but its Township XP, GP and Slayer Coins follow your current levels. The Casual tasks page states each reward's rule in the game's terms.

Worked example: Give 100 Normal Logs to your Town. It needs 100 Normal Logs, and its rewards read: Township XP, 9% of the XP to the next Township Level; GP, 5 × the XP reward; Wood, 2,500, up to free storage.

The game's own run of this task paid 7 Township XP and 35 GP at Township level 1, and 976,830 XP and 4,884,150 GP before modifiers at level 120. The 2,500 Wood was the same both times, so a casual task cleared early is worth little GP, while the same task late pays millions.

Tasks that list Slayer Coins pay 1,000 × Slayer Level, such as Give 750 Stardust to your Town: at Slayer level 120 a listed 3,000 becomes 120,000.

Find this task on the Casual tasks page