It's always a pleasure to see you and I hope I'll be able to repay your hospitality if you ever come to visit us in Cambridge.

repay 由前缀 re-（表示"再次"或"回"）和动词 pay（支付）组成，字面意思是"回付"，引申为"报答、回报"的意思。在这里指用同样的热情好客来回报对方的款待。