If you want a new raspberry pi 4 8GB today, you basically have to buy from a scalper at a cost of around $200 [1]

Or you can try to monitor https://rpilocator.com more than the scalpers do, and you might be able to get one for $100 instead.

[1] https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2380057.m...