You can expect Babbel to set you back at around $13.95 per month. They also offer discounts if you buy blocks of months together, such as getting a percentage off for purchasing three or six months on Babbel.
They also offer sales throughout the year where you can get 30% off, such as their summer sale.
You may also be able to get discounts and deals if this is something you are pursuing through your job. For example, they offer Babbel for Business packages that can be tailored to the needs of your business for competitive prices (depending on your package).