Andrew Mickel of multi-award-winning firm Mactaggart & Mickel said that the scheme might not have run into problems so quickly if it had been targeted solely at first-time buyers and lower-cost properties.
Last week, it emerged that the scheme had virtually run out of money for this financial year, just three months into a new funding round.
According to reports, all the money earmarked for central Scotland has now been allocated and there are just a few remaining deals still available to people in the Aberdeen, Inverness and Orkney areas.
Most people who had hoped to use the scheme before next April will now have to find the extra money elsewhere or see their house deal fall through.
Under present rules, the scheme can be used to help buy a home up to a maximum cost of £400,000 - more than twice the average price of a Scottish home, at £162,000.
Although lower than the £600,000 maximum limit of the English version of the scheme, Mickel said that - given the limited funding for the scheme in Scotland - he did not understand why the limit had been set so high.
He commented: "First-time buyers or those looking for cheaper properties are not put any higher in the queue than those wanting a £400,000 house."
Since its introduction last September, demand for the Help to Buy scheme has, according to the Scottish Government, been "extremely high" and has so far helped more than 2000 people buy a home.
A Scottish Government spokesman told the Sunday Herald that the £400,000 limit meant that the scheme covered around 90% of the newbuild market north of the Border and also that the Scottish market was not put at a disadvantage against the English scheme with its higher limit of £600,000.
Mickel said that the news that funding has dried up for this year had taken the housebuilding industry by surprise.
"We have been dealing with quite a few upset clients this week," he said. "For most people, buying a home is a life-changing event. This news has been hugely disappointing for them.
"We didn't expect the money to run out quite as quickly as it did, and there was little warning that this was going to happen from the Scottish Government."
One gripe of the housebuilding industry in Scotland has been the fact that the scheme - designed to boost housebuilding and home ownership during the protracted recession - was rolled out six months later in Scotland than south of the Border, where it was launched in April 2013.
To add to that, it now appeared that the Scottish version of the scheme has been more precariously funded than the version in England and Wales, where funding is in place until 2020.
In total, £275 million was set aside to fund the scheme by the Scottish Government: £35m for 2013-14, £140m for 2014-15 (including an additional £50m announced by Deputy First Minister Nicola Sturgeon in May) and £100m for 2015-16.
Mickel said: "One of the questions that we would be interested to explore is whether the Government can bring forward to this year any of the £100m it has allocated to fund the scheme from April 2015.
"Help to Buy has been a game-changer for the industry. It has moved everything forward and brought more confidence and momentum back into the market, but now we learn that the scheme has run out of money.
"We would much rather have steady, sustainable growth without peaks and troughs. To have a stimulus package that has come to a juddering halt until April next year is not helpful." According to the Scottish Government, 180 homes valued between £300,000 and £400,000 have so far been sold under the Scottish Help to Buy scheme, representing around 9% of total sales to date.
A spokesman said: "The Scottish Government developed and monitors the scheme along with Homes for Scotland and the Council of Mortgage Lenders to ensure it meets the needs and priorities of the Scottish market.
"We are considering whether there is any scope to provide limited further support this year but no decision has been taken."