But who are the very best, and absolute worst, arrivals at St James’ Park since the month of mid-season shopping was introduced in 2002-03?
Here we take a look at five who proved value for money – and another five who didn’t!
January TOP FIVE
1: Moussa Sissoko £1.8m – 2012
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The French midfielder was signed on a six-and-a-half year deal from Toulouse.
And although Sissoko’s early form at Newcastle undoubtedly dipped – particularly under Steve McClaren – he ultimately proved a decent buy on the pitch, and a sensational one off it.
After 133 appearances for United, which produced 12 goals and 19 assists, Sissoko was sold to Tottenham in the summer of 2016... at a profit of almost £30m.
2: Papiss Cisse £9m – 2012
During his three years on Tyneside, Cisse scored 44 goals in 131 matches and produced 10 assists.
But while those figures look decent, they barely tell the story of his early impact at Newcastle.
An astonishing 13 goals in his first Premier League games – including two outrageous strikes in a victory at Chelsea – fired United to a surprise fifth-placed finish and into Europe under Alan Pardew.
3: Martin Dubravka loan – 2018
Unknown to the vast majority of Newcastle fans when plucked from the Czech league on loan with an option to buy, Dubravka made an immediate impression… and then some.
In possibly the finest debut performance by a United goalkeeper, Dubravka repelled Jose Mourinho’s Manchester United, and had Geordie fans hurriedly rewriting The White Stripes’ “Seven Nation Army” in his honour.
Having done more than enough for his stay at St James’s Park to be made permanent in the summer of 2018, Dubravka has remained a fans’ favourite.
4: Hatem Ben Arfa £5.4m – 2011
Despite first arriving on Tyneside the previous summer, France international Ben Arfa makes this list because he only signed permanently for Newcastle in January 2011.
And while his wizardry proved fleeting, the value for money he offered remains undeniable.
In support of Demba Ba and later Papiss Cisse, Ben Arfa produced five Premier League goals and six assists in 2011-12.
Debate still rages over whether his league goal against Bolton or FA Cup winner against Blackburn was the best scored at St James’s Park in the last decade.
Ben Arfa’s form, waned as Alan Pardew tinkered with tactics and key players were sold, but the winger remains a hero on Tyneside.
5: Mathieu Debuchy £5m – 2013
Another player whose impact more than paid off his transfer fee, and earned Newcastle a handsome profit.
Debuchy, a former teammate of Yohan Cabaye at Lille, swiftly showed his pace and overlapping ability in an Alan Pardew team that was generally on the wane.
Arsenal liked what they saw, and paid around £13.5m to take him to the Emirates after 18 impressive months on Tyneside – and a goal in a Tyne-Wear derby defeat at the Stadium of Light.
January BOTTOM FIVE
1: Jean-Alain Boumsong £10m – 2005
Six months after Glasgow Rangers signed him on a free transfer, the French defender made a surprising move to Newcastle.
But a nightmare, error-strewn spell at St James’s Park came to epitomise United’s struggles under Graeme Souness.
The manager did not help himself by blaming Boumsong’s troubles on Newcastle’s struggle to find football boots to fit him.
Sold to Juventus (they were in Serie B at the time) in the summer of 2006 at a huge loss, Boumsong moved on to Lyon before finishing his career in Greece with Panathinaikos.
2: Henri Saviet £5m – 2016
Bought by Steve McClaren to fight what would be a failed relegation battle, Sengalese international Saivet produced a decent impression of the Invisible Man.
After just 148 minutes of Premier League football, the midfielder left for Saint Etienne on loan, where he remained while Rafa Benitez took United back into the Premier League.
On his eventual return, Saivet played – and scored – against West Ham just before Christmas 2017.
But he was then shipped on loan to Sivasspor in Turkey, and is now at Burssaspor – yet again on loan – as his value wanes ever further.
3: Islam Slimani loan – 2018
While one January 2018 loan signing – Martin Dubravka – has earned near-legend status on Tyneside, Slimani goes down as a huge disappointment, and a staging post in the road to Rafa Benitez parting ways with Newcastle.
Benitez’s frustration at being denied mid-season funds to buy a striker as United fought to consolidate their return to the Premier League had mounted throughout the month.
And it was having been forced to borrow the injury-plagued Slimani from Leicester in the final hours before the transfer window that the Newcastle manager privately briefed the media over his frustrations with the running of the club.
Slimani proved every bit as underwhelming as Benitez perhaps expected, starting just one Premier League game for United.
4: Seydou Doumbia – loan 2016
Three Premier League appearances, 29 minutes and barely a meaningful touch of the ball are the uncomfortable details of Doumbia’s bizarre spell on Tyneside.
He arrived at St James’ Park off the back of 11 goals and five assists in 21 games for CSKA Moscow and a career goals record significantly better than one every other game.
But having looked desperately short of touch on his debut as a late substitute in a hammering at Chelsea, Steve McClaren gave the Ivory Coast international short shrift despite Newcastle’s desperate search for the goals to keep them up.
Gallingly, Doumbia showed up at FC Basel the following season and scored 20 in 25 league games.
5: Mapou Yanga-Mbiwa £7.2m – 2013
Unlike the other players on this list of stinkers, Mbiwa began his Newcastle career in superb style.
Having come off the bench late on in a Premier League game at Aston Villa, he produced a couple of superb defensive interceptions to secure a 2-1 win.
His pace and athleticism appeared sure to be a huge asset, and he also showed his versatility by performing at both centre-back and left-back during the 2013-14 season run-in.
But a loss of form and confidence as the following Christmas approached proved terminal, and Mbiwa was loaned out early in 2014-15 to Roma, where he did enough to earn a permanent move in January 2015.