The Lord of the Rings Online

The game is free-to-play with an optional subscription fee and premium item shop.

Premium currency

Almost all purchases in the game are made via a premium currency called "LOTRO Points". These points are sold in inconvenient bundles where 1000 points equal roughly 10 USD. Bundles come in sizes of 600, 1600, 3150, 6300, 11000, or 23000, with larger bundles granting slightly more points relative to the price. Bundle sizes are quite awkward in that many items fall right in between them.

LOTRO Points can be earned through regular in-game play as well, mostly through completing "deeds". These are achievement-like activities. Some might be as simple as entering a new zone, whereas others can be more involved, like needing to perform certain long quest lines or killing hundreds of enemies of a certain type. Many of these objectives are completed automatically as you play the game without having to put in any extra thought. Points are earned at a somewhat steady pace, allowing you to purchase premium items periodically, but expecting to purchase every item in the store through only free-to-play means is unrealistic.
Early on in the game you will obtain a quest that requires usage of the premium store directly in order to purchase a mount; however, you are given enough LOTRO Points to purchase this mount without needing to spend money.

Next to LOTRO Points the game also sells Mithril Coins, which are bought with LOTRO Points. These coins are used for in-game purchases outside of the premium store. They are used for convenience items as well as cosmetics, among other things. An example of convenience items is resets for timed quests. Some quests can be completed once per day; however, with Mithril Coins the quest can be reset right away. Another example is fast travel, which can be purchased with in-game money or with Mithril Coins. The game contains more such options, where you can either pay with in-game coins or Mithril Coins.

Premium store

The premium store holds many different kinds of items, most of which are focused around convenience. The game contains many systems that are quite slow and time-consuming by design. Some of that is inherent in the nature of MMORPGs, but others seem to be specifically designed around needing premium purchases. Convenience items include things like temporary XP boosts, larger inventory sizes, crafting speed boosts, fast travel locations, reduced cooldowns on travel, discounts on all in-game shops, faster mount riding speed, and more. If there is a system you find slow or inconvenient, there is bound to be a premium item that alleviates or bypasses this system to some degree.

Some items also allow you to bypass certain restrictions directly. For instance, you can obtain a maximum of three crafting professions, but you can buy one more slot through the premium store for 995 LOTRO Points (roughly 10 USD, but requiring the 15 USD bundle).

The store also offers many purchases that bypass the game's mechanics directly. For instance, you can instantly level up to varying levels. This starts at leveling up to level 50 for 3995 LOTRO Points (roughly 40 USD, but requiring the 50 USD bundle), up to level 140 for 6695 LOTRO Points (roughly 70 USD, but requiring the 80 USD bundle).
You can also instantly level up crafting professions.

The game also includes some items that directly grant power. The store offers "Stat Tomes", which permanently increase certain stats. Other items include healing and power potions, potions that increase the drop chance of certain items, and improved food items.

The store also offers many cosmetic items. These include emotes, pets, mounts, armor, and more. The price of these ranges widely from 250 LOTRO Points for smaller items to 2495 points for some of the better mounts.

The store also sells game expansions. These include smaller quest packs as well as full-on expansions. Some of the smallest quest packs sell for 295 LOTRO Points, with larger packs selling for up to 1695 points, with varying degrees in between. Purchasing all quest packs individually costs over 22,000 points, which would require the 160 USD points bundle. However, it should be noted that all quest packs are included with the VIP subscription.
Expansions sell for 2995 points each. Most expansions are included with the base free-to-play game. Only the latest expansions need to be purchased, with currently two being available.

Most playable classes are included with the base game, but two of the most recent classes, Brawler and Mariner, do need to be purchased separately for 1000 points each.

The game pushes premium store purchases quite heavily. For instance, each time you complete a deed you are prompted to visit the store, a store button is always visible in the UI, and loading screens almost always contain advertisements for certain services. Additionally, sometimes you may loot special item boxes that require a key to open. The key can only be obtained via the premium store.

VIP Subscription

The game offers an optional subscription fee. It is priced at roughly 13 USD per month, or less if you pay for more months in one go. This subscription largely consists of convenience items but also includes a large amount of playable content, including all quest packs.
Some of the benefits include: 500 LOTRO Points per month, access to special servers, increased character slots, increased inventory slots, swift travel to more zones, daily bonus XP, more auction listings, limitless in-game chat, access to in-game mail and bank from anywhere, no maintenance charge for in-game housing, and more.
Some of these benefits remain even if you choose to no longer subscribe, such as the increased inventory size.

Playing the game entirely for free is feasible, but you will do so at a much slower and more inconvenient pace than others. While many items are entirely cosmetic or largely remove inconveniences, some items also include increased power. There are no items that are decidedly pay-to-win, but the benefits some items grant cannot be overstated. Those who choose to pay will have an easier time than others when it comes to certain game mechanics. The game does not have a heavy focus on player versus player or high-skill co-op content; as such, no purchases other players make will have an impact on your own experience. It's up to you to decide if the unfair and slow nature of some mechanics hampers your experience.
The vast array of inconvenient system that can be bypassed with real money purchases may be off-putting to many players, but the equally vast amount of free content should not be understated either.