Thanks as always — come again!

Literal

Every-time, again come.

Shopkeeper's farewell. 毎度 abbreviates 毎度ありがとうございます ('thank you as always') — the classic merchant's phrase. いらっしゃい is the bare imperative of いらっしゃる (the honorific for 来る / 行く / いる), used specifically as a welcome or 'come again' in shops and restaurants. Culturally tied to the 下町 merchant register — friendly, warm, unpolished by 'official' keigo standards.