That's a hefty asking price for a feature Twitter just rolled out in July. BuzzFeed News reports that advertisers have to spend at least $500,000 to launch a Promoted Stickers campaign—though that money can be used on other ad products as well, like Promoted Tweets.
This is also surprising because Twitter has reportedly been decreasing the minimum ad spend for other advertising products. From BuzzFeed:
The $500,000 minimum comes at a moment when Twitter has been lowering its minimums on other ad products, BuzzFeed News has learned. "I think they are beginning to realize that the barriers to entry have historically been too high for a lot of the products," one advertising executive told BuzzFeed News. "I was surprised that they came in at such a high figure with this."