As a result, the experimental "superteachers" are unlikely to do any of the advisory and consultancy work that forms an integral part of the scheme when it starts next month.
The Government has set aside o400,000 from the standards fund to pay for the first year of advanced skills teachers, who can be paid up to o40,000.
But with ministers set to approve more than 100 bids from 70 schools, headteachers' leaders are warning that the true cost will be three times this amount.
This is likely to mean that any outreach work by the ASTs must be funded by local education authorities - which would have to pay for supply cover.
At the same time, education action zones will be expected to bear the full costs of any advanced skills teachers in their areas.
"It could be a mite embarrassing," said David Hart, the general secretary of the National Association of Head Teachers. "The AST grade has not been thought through. In reality, the cash for this will have to come from other budgets.
"If this scheme really is to become an alternative to management, it's going to make a big dent in the Chancellor's o19 billion."
News of the scheme leaked out last month when it emerged that ministers had approached 290 specialist schools asking them to take part.
It is understood that 70 put in bids for a total of 110 expert teachers, more than one per school. The Government has capped this figure at 103.
The technology colleges and other specialist schools which were invited to take part in the pilots were offered o5,000 per year for two years in extra salary, the same amount in supply cover plus a single o5,000 grant for setting-up costs.
Applicants will be interviewed and observed in the classroom by a private inspection company, Westminster Education Consultants.
Teachers will have to prove they excel in: getting results, subject knowledge, lesson planning, motivating pupils, maintaining discipline and supporting colleagues.
For a salary of up to o40,000 ASTs are expected to work with teachers in other schools.