I agree that we haven't got endless money but there's obviously still money available to spend.
The whole 3 out of 4 targets suggests that there's a budget this window that hasn't been fully spent. At one point we were close to 100 million for Griezmann plus wages. Maybe the Lukaku deal hit took a chunk of that money, but also maybe not. We were getting a forward and a winger in those 4 targets. The Perisic pursuit was around 40-50 million plus wages, his on a reported 90k at Inter so that wasn't going to a cheap contract. So when you factor that all in, a Mahrez deal isn't really pushing any boundaries that wasn't set before hand.
I agree Mata will probably leave next summer and a trip back to Spain would suit. His done a good turn at us no doubt and it feels like his really embrace the club and it's fans. The Lingard contact still keeps me awake at night it's awful. My only hope is that next season someone like say Leicester could save us from that. But he seems more then happy at the minute taking his 100k a week, sitting on the bench, and working out handshakes for everyone.
Overall point being that Mahrez or even Alexis could come now because I feel like we'd budgeted for 4 stellar signings before we even agreed who had to be sold. We've taken the rooney wages off our books and Zlatan is coming at half the cost so there's wages there.