The Turbine Store (http://store.turbine.com) is operated by Digital River, a third party contracted by Turbine. They have more payment options available. You select the items you want to buy, and if you don't have an account with Digital River when you checkout you will create one then. Do NOT use your LOTRO login. Turbine does not share any of your account information with Digital River. When you make the purchase, you will be emailed the product keys for the items, which need to be added to your Turbine account (https://myaccount.turbine.com). You can buy multiple copies of the same thing at once for multiple accounts/subscriptions, or even give a key to someone else.
The LOTRO Market (https://store.lotro.com) is operated by Turbine. It requires you to be logged into the account/subscription you want the purchase to go to. The items bought are auto-applied to the account/subscription you are logged into. If you have more than one, you need to log into each and make a separate purchase for each. You cannot buy for someone else.
"Everyone's got one. Better to be a smart one than a dumb one." - me
"It's people like you that [I]think[/I] you know everything that give those of us that [I]do[/I] a bad name." - me
"Eat, drink, and be Merry, 'cause Pippin was a fool of a Took."