I think the only savings you can get is if you level all your guys to 60 and wait until the end to buy the expansion. Hopefully by then the price will be lower (it will go down eventually) or you will find it on sale or get gift cards or get it as a gift.

Not sure I fully understand your transfer scheme though. You currently have 5 accounts but want to RAF up 5 teams of 4? Wouldn't you just need to buy 2 more accounts and RAF them to two current accounts? although, you miss out on some level gifting.

If I understand you correctly, I think you just need 2 (or 3 if you really want the levels to gift, but one account will always lose out regardless) accounts to boost up 4 toons (however many times) to 60. You don't need any expansions on the new accounts at all for this or are you saying you don't have WoTLK on three of your current accounts?