The authority, which is under huge financial pressures, agreed last month to take 15 unaccompanied asylum seeking children (UASC) up to the 2019/20 financial year as part of the National Transfer Scheme.
The council will take five a year, starting in 2017. Now the full costing has been revealed, bosses at the authority say it would bring 'significant challenges and unbudgeted cost pressures'. By 2020, the authority says it would have spent £1.37m towards these asylum seekers –averaging out at more than £90,000 per child.
Councillor Sean Coughlan, the Labour leader of Walsall Council, said: "The cost is a concern. The Government is making decisions and not following up on them. We have not taken any children from this process yet and until we do we will not know the full impact of the costs. No one can imagine what these children will have gone through and their needs far outweigh the figures."
But UKIP West Midlands MEP Bill Etheridge has criticised the move. He said: "Whilst it is a noble thing, to do it at a time when you cannot provide basic services to your own people due is irresponsible and plain stupid."
The figures were raised at an Education and Children's Services Overview and Scrutiny Committee, where members were sympathetic but did question the costs involved.
A report prepared for the meeting last week explained: "It is currently considered that UASC would place significant challenges and un-budgeted cost pressures on the council."
A spokesman for the authority said: "The £1.37m reported is the cumulative net cost the council is forecasting to spend by 2019/20, after taking account of the Home Office contributions towards gross costs."
The home office provides funding of up to £114 a day for asylum seeking children under the age of 16. But when a child reaches 18, this figure is capped at £200 a week. Finance bosses at Walsall Council have assumed that the children will arrive older than 18, as they still count as UASC if they apply before their 18th birthday or turn 18 while they are in the borough.
They have also assumed that least five of the 15 will be complex needs, therefore requiring extra special care.
Money goes towards schooling, accommodation and helping the asylum seekers with any needs or issues they have.
It comes at a time when the council is looking to save £86 million in four years. In plans out for public consultation it has proposed closing 14 of the borough's 15 libraries, relocating the leather museum and the local history centre, ceasing funding to the New Art Gallery, putting up parking charges and introducing a charge for garden waste.
Elsewhere, Staffordshire County Council has already taken three UASC and has pledged to take more. But did not say how many more and how much it would cost.
Dudley council confirmed it was not part of the scheme while Sandwell and Wolverhampton Councils were unable to comment.