Paris Saint-Germain ushered in a new era of huge spending after last summer's transfer window exploits. 

The French club bought Neymar from Barcelona for a world-record fee of £198 million, and also secured left-back Yuri Berchiche for over £14 million.

Of course, on top of spending over £200 million on two players, PSG also took Kylian Mbappe on-loan from AS Monaco. 

The 19-year-old was one of Europe's hottest prospects last summer, coming off the back of a brilliant season with Monaco, who he led to the Ligue 1 title. 

And it's fair to say he's continued his fine form after moving to the French capital. 

Mbappe has become part of a deadly attacking trio alongside Neymar and Edison Cavani. Between them, the three have over 70 goals after six months of playing together. 

While negotiating the loan deal for Mbappe, PSG agreed on a price to pay Monaco if they wanted to make the deal permanent for next season. 

The price tag was made £166 million and after the Ligue 1 leaders beat Strasbourg 5-2 at the weekend, they've activated a strange contract clause that means they now have to make Mbappe's move permanent. 

Three more points on Saturday meant that, unsurprisingly, it's mathematically impossible for PSG to be relegated. 

According to the Daily Mail, a clause in Mbappe's deal means that now they've confirmed Ligue 1 football next season, they're obliged to make the forward's move permanent next summer.   

PSG will be happy to pay the £166 million fee, considering the Frenchman has 15 goals and 14 assists in all competitions so far - not bad for someone that's so young.

However, if Mbappe hadn't been performing so well for Unai Emery's side, it would have been interesting to see him go permanently for that much at the end of this season, as the clause would have been met anyway.

Instead, PSG are spending a huge amount on a young player they will feel can grow into one of the world's best over the next few years. 

And in today's market, his price tag isn't going to be criticised, especially given that some of Europe's elite teams will no doubt spend similar money on other players.  

Is Kylian Mbappe ever going to be worth £166 million? Have YOUR say in the comments below.