The Swiss team were struggling financially at the beginning of the year, but were taken over during the summer months, securing their future.
However, they have since decided to take 2016-spec Ferrari engines for next year, a move they insist is not financially motivated.
It is also a decision which has perplexed Tost, whose Toro Rosso team have struggled with un-developed year-old Ferrari engines this year.
"I don’t know all the reasons and background stories why Sauber decided to go with this year’s engine," he said. "I wouldn’t like to be in this situation because it’s a big disadvantage on the performance side to run with last year’s engine."
There had previously been moves to block engine manufacturers from supplying older engines, but although Tost sees the disadvantage they give, he does think it is something which should remain on the table for everyone.
"From the regulation side, I think it should be kept open because a one year old engine is most-often cheaper than the newest specification," he said. "From the performance side the team anyway is disadvantaged, therefore, the regulation should allow it."
Meanwhile, Toro Rosso will return to using current specification Renault engines in 2017.
Bahrain International Circuit - Winter testing