Striking the right deal in the transfer market can be a difficult process. Selling clubs will try and extract every possible penny from any deal, while those buying will not want to pay over the odds for a player.
The process can often become even more difficult depending on the age of the player involved. Younger ones often command higher fees, although there can be some risk in signing someone with a lack of experience. On the other hand, older pros may not have much resale value.
All of those rules have applied to Irish players down through the years.
We have looked back through the years to find the most expensive deals involving players from the Republic of Ireland, at every age from 18-years old up to 35-years old.
Unsurprisingly, some big names are included on multiple occasions.
Most Expensive Irish Player At Every Age
18: James McCarthy (Hamilton to Wigan Athletic) - £3million
James McCarthy broke the previous transfer record for an Irish record for a player aged 18 or under when he joined Wigan in 2009, beating the mark Anthony Stokes set when he moved to Sunderland a few years prior.
As you will see in a moment, Wigan would sell him on for a sizeable profit some time later.
19: Robbie Keane (Wolves to Coventry City) - £6million
Robbie Keane still holds the title of 'most expensive Irish teenager' thanks to this move in 1999, which also represented a then British record fee for a player yet to reach their 20s.
This will not be the only time the striker features on this list.
20: Robbie Keane (Coventry City to Inter Milan) - £13million
Keane only stayed at Coventry for one year before moving to Inter Milan. While things wouldn't quite work out for him in Italy, the Serie A side managed to recoup nearly all of the fee they paid for him after selling him to Leeds the following summer.
21: Roy Keane (Nottingham Forest to Manchester United) - £3.75million
This was a big fee to pay back in 1993, but it is very surprising that no 21-year old Irish player has moved for more during the intervening years.
It's fair to say that Manchester United got decent value out of this deal in the end.
22: James McCarthy (Wigan Athletic to Everton) - £13million
Wigan would make a big profit on James McCarthy, pocketing around £10million from the deal to sell him to Everton four years after their original purchase.
23: Robbie Brady (Hull City to Norwich City) - £9million
Robbie Brady impressed after joining Hull City on a permanent deal, so much so that it convinced Norwich City to fork out a near club record fee to bring him to Carrow Road back in 2015.
24: Damien Duff (Blackburn Rovers to Chelsea) - £17million
This is the second highest fee ever paid for an Irish player and it is likely Blackburn could have got even more out of Chelsea had it not been for the release cause in his contract.
Duff would win two Premier League titles at Stamford Bridge.
25: Robbie Brady (Norwich City to Burnley) - £13million
A second appearance here for Brady, with Burnley splashing out a club record fee to sign the midfielder six months after his performances for Ireland at Euro 2016.
26: Shane Long (West Brom to Hull City) - £7million
Arriving in January of 2014, Shane Long was signed by Hull City in an effort to stave off relegation.
While they wouldn't manage to do so, the Irishman's form was good enough to see them sell him for a profit a few months later.
27: Shane Long (Hull City to Southampton) - £12million
Shane Long was very much in demand in his mid 20s, with Southampton having to pay £12million to sign the striker after Hull's relegation at the end of that campaign.
28: Robbie Keane (Spurs to Liverpool) - £19million
Robbie Keane's move to Liverpool in the summer of 2008 remains the most expensive deal involving an Irish player.
Of course, he would last only half a season at Anfield before returning to Spurs.
29: Richard Dunne (Manchester City to Aston Villa) - £6million
Richard Dunne was a casualty of Manchester City's recently found wealth, moving to Aston Villa in the summer of 2009.
That fee would prove to be quite the bargain, with Dunne being named in the PFA Team of the Year during his first season at Villa park.
30: Darren Randolph (West Ham to Middlesbrough) - £5million
Randolph was no longer first choice at West Ham by the summer of 2017, but Championship club Middlesbrough still forked out a sizeable fee to bring him to the club.
31: Robbie Keane (Spurs to LA Galaxy) - £3.5million
A fourth and final appearance for Robbie Keane on this list, his £3.5million move to LA Galaxy turned out to be quite the success.
He would continue to star for Ireland after his move to the US in 2011, also winning three MLS Cups during his time in California.
32: Shay Given (Newcastle United to Manchester City) - £6million
Shay Given holds the record as the most expensive Irish players in their 30s, moving to The Etihad in the winter transfer window in 2009.
33: Daryl Murphy (Ipswich Town to Newcastle United) - £4million
Daryl Murphy was seen as the ideal Championship striker when he was signed by Newcastle in 2016, scoring five goals for the club as they were promoted to the Premier League.
34: Daryl Murphy (Newcastle United to Nottingham Forest) - £2million
Murphy would last only one season at Newcastle, leaving for Nottingham Forest the following summer.
35: Shay Given (Manchester City to Aston Villa) - £3.5million
Aston Villa clearly saw plenty of life remaining in Shay Given when they signed him at the ripe old age of 35.
They got decent value for the fee as well, with the Donegal man spending four seasons at the club, although mostly as a backup.