One advantage of light rifles is that you can use somewhat larger, heavier scopes for better low-light performance and/or reliability without the total weight being too burdensome.
Choose a scope for each rifle that best suits its purpose and forget the swap-a-scope idea. Spend the most on the scope for the rifle you use most, then shop for used, bargain, or close-out scopes for the others until you can afford better. I've got a number of decent reliable scopes that cost less than $200 new. Do some research, pick the ones that fit your requirements, then shop around for deals.
Amazon, Natchez, and some others have stuff on sale all the time, and don't forget our pal Doug from Camera Land, who regularly posts good deals.
