A crochet along can be hosted in real life or digitally on a platform like Instagram, Facebook, Ravelry, Youtube, or a blog. There are also crochet alongs that do not require you to have a social media account. These crochet alongs are usually hosted through an email list, on Youtube or in real life.
The cost of participating in a crochet along depends on the host. There are both free and paid crochet alongs and the price can vary between a couple of euros to up to 30 euros. The price is up to the host and often reflects the pattern's complexity and the item's size. There are also crochet alongs that include a yarn kit and that of course increases the price.