They're lucky in that in the early days where Roman pumped in the money before FFP came into play they’ve been in a pretty self sufficient position in recent years because they’re able to sell players at high prices which therefore allows them to buy at high prices.
Last summer they sold Hazard for a rumoured total fee of £140m and this summer Atlético paid the obligatory purchase fee from the Morata loan which is about £50m. They’ve also sold a bunch of fringe players over the last 12 months too that’s probably netted them a combined £30m. So give or take they’ve had around £220m to splash over the last 12 months combined. They signed Kovacic permanently last season for £40m and then this season, the signings of Ziyech, Chilwell, Werner and Havertz have equalled to roughly £210m. So in the past 12 months they‘ve only got about a £30m net spend.