It sure does. Every time you add a quantity break price to an item, it doubles the original number of variants.
Let's say you have a product that has 2 options: Size and Color.
SIZE: SM, M, L, XL
COLOR: Red, Blue, Green, Yellow
If every color is available in all the sizes this product will have 16 variants. There are 4 sizes and 4 color options so a total of 16 different choices, or variants. When you then apply a quantity break price to this product it would create a duplicate hidden variant for each of those options, so you would then have 32 variants. If you added another you'd have 48, and another 64, and so one.
Shopify only allows 100 variants per product.
So sometimes this becomes an issue when the app is trying to create the price tiers and runs out of variants available. If this happens, the app will skip the product when trying to create them and send you an email notification listing the product that was the issue. Also, keep in mind your Shopify plan has a limited number of variants as well depending on what plan you are on. So even if you don't max out the product's variants, you might max out your overall variants. To fix that you just need to upgrade your Shopify plan to one that allows more variants.
But there's another way!
We created an app called the Product Options app that allows you to create an unlimited number of options for products and they don't count as variants. If you need to have many different options and quantity breaks we recommend using the Product Options app to handle the options for your products. You can learn more about that app here: http://apps.shopify.com/product-options