I can’t promise anything, but it appears that the five new books will mass about 900g all told including the mailer. Maybe a bit more, maybe less. That’s about £6 shipping to the UK, maybe £10 to the EU, and maybe £13 to non-EU and beyond. USA folks get media mail from my house. That’ll be about $6.
If it’s more than I think, and the prices change, I’ll let you know. But this strategy has worked for me recently for the Nordlond Sagas campaign, and was highly satisfactory for both price and speed.