I have 2 Garmin devices. I have one device with the lifetime maps and another doesn't. I was wondering how can one copy maps from one device to the other?

Reading various threads on this board says that the maps are device locked. Is there any method to unlock those maps? Can anyone direct me to related write-up, if available?

Many thanks in advance.

(P.S. - Pls dn't suggest me to buy new maps or use OpenStreet maps. I would have bought new maps if the price was reasonable but the cost is $50+, which IMHO is totally unreasonable. Hence all the trouble.)