According to Richard Parry and Tom Collomosse of the Evening Standard, Barkley has just one year remaining on his deal at Goodison Park and could well be on his way this summer.
Indeed, per the Telegraph's Chris Bascombe, Everton boss Ronald Koeman believes his departure to be a realistic possibility:
Chris Bascombe @_ChrisBascombe
Koeman asked if confident Barkley will stay. “No.”2017-5-19 12:04:47
However, while he is "a firm favourite among the Tottenham hierarchy," such a valuation will prompt them to look at other targets if Everton aren't willing to budge.
Per Parry and Collomosse, Sigurdsson is among several options Spurs will consider in Barkley's stead and could cost half as much.
The Iceland international spent two seasons with Spurs and made 83 appearances, but he struggled to establish himself in the starting lineup and returned to Swansea in 2014—a move Spurs boss Mauricio Pochettino would have preferred not to take place.
Sigurdsson has enjoyed another excellent campaign with the Swans and was voted by his peers as their Player of the Year:
Swansea City AFC @SwansOfficial
🏆 The winner of our Players' Player of the Year goes to... Gylfi Sigurdsson! 👏❄️ https://t.co/tsqfHlbKJz2017-5-17 20:53:05
He's an incredible playmaker with an eye for goal, too—particularly from set pieces—and he also puts in an enormous amount of work. Earlier in May, TalkSport reported he had covered more ground than any other player this season having run 255 miles, just ahead of Spurs' own Christian Eriksen.
Here's a look at his numbers this season compared with Barkley's, courtesy of Squawka:
|Sigurdsson vs. Barkley 2016-17 Premier League Stats|
|37 Apps||34 Apps|
|3,237 Mins Played||2,746 Mins Played|
|9 Goals||5 Goals|
|13 Assists||8 Assists|
|70 Chances Created||80 Chances Created|
|29 Take-Ons||63 Take-Ons|
|29 Tackles||26 Tackles|
|5 Aerial Duels||37 Aerial Duels|
|34 Interceptions||13 Interceptions|
|78% Pass Completion||83% Pass Completion|
The Everton midfielder has at times struggled for form and consistency this season but overall had a good campaign and most notably showcased some outstanding creativity in the final third.
Both he and Sigurdsson would make strong acquisitions, but neither would be able to command a starting berth in this Spurs side ahead of Dele Alli or Eriksen.
Bleacher Report UK's Sam Tighe expressed his doubts about the latter:
Sam Tighe @stighefootball
Blimey Glen. Yes Sigurdsson is good but he definitely does not walk into any of the top six PL teams. Not 100% sure he gets in ANY2017-5-6 16:43:14
Sigurdsson would still perhaps be the better choice of the two—particularly at the reported transfer fees—and further strength in depth would only enhance Spurs' credentials, but he may not accept a role as a squad player again.
As for Barkley, Spurs are right not to pursue him if Everton demand £50 million—such a fee is far too high to pay for a player who doesn't even improve their starting XI, let alone one who has only one year remaining on his current contract.