Trainers are NPCs that help increase proficiency in certain skills in The Elder Scrolls V: Skyrim. The cost of training a skill up to level 51 is 10*[skill level]+50, but from level 51 onwards the training cost triples to 30*[skill level]+50. Remember you can only train up to 5 times every level, with any trainer.
Adepts can train players to level 50, Experts to level 75, and Masters to level 90. Once your level reaches higher than a trainer, the option for training disappears. Unlike Oblivion, there is no means to be trained all the way to level 100 in a skill. The more advanced the training is, the higher the price will be for the training.
This can be somewhat exploited and give you free training if your follower is also a trainer. There are only six trainers who are known to be followers, though. They are: Aela the Huntress (Archery Expert), Njada Stonearm (Block Expert), Farkas (Heavy Armor Master), Vilkas (Two-Handed Master), Athis (One-Handed Expert), and Faendal (Archery Adept).
Angi at Angi's Camp will train you, for free, any 6 levels of archery. However, you must pass her tests. At the end of the final test, you receive Angi's Bow.
Riften in The Ragged Flagon (note the only trainer in skyrim that can train you to be lvl 100 in a skill but for a great cost usually at upwards of 4-5 thousand, even with the best speech benefits. It should also be noted that pickpocketing is one of the easiest skills to level, and pickpocketing a few expensive items will level you equally.)
Trainers that are also merchants, such as Arcadia in Whiterun, end up with the gold paid to them for training in their inventory. One can easily recover gold spent on training by selling them items. This must be done immediately, if the player leaves, the extra gold may not be there next visit. Player can also pickpocket the gold back from the trainer, increasing his skill in pickpocketing too. It is advisable to pick his pocket after every one or two trainings as it can get very difficult to take a larger sum if the character doesn't have pickpocket perks.
