In the federal system, broad classes of crimes ("murder", "robbery", "wire fraud") have been assigned maximum sentences. For example, under no conditions can a sentence for wire fraud exceed 20 years (you get to the theoretical max of 35 in this case by adding the other charges, but they in the case everything would likely be folded into wire fraud on sentencing because all of the charges were based on the same conduct).
But most defendants convicted of wire fraud (even by a jury) don't serve 20 years. In fact, many first-time offenders don't serve anywhere close to that -- it's usually under a year.
Instead, the Federal Sentencing Guidelines [1] are a mostly-mandatory (there are constitutional reasons why judges are allowed to depart from the Guidelines, but it's rare and requires justification) system to calculate a range that a defendant will actually serve following a jury conviction.
Here, wire fraud is a "level 7" offense.[2] That offense level can be adjusted upward or downward based on other facts of the crime (e.g., was stock fraud involved? add 4). Assuming that Orrin Kerr was right and the total loss was $5,000 or less, there would be no adjustments and so Aaron's offense level would be 7.
Take that to the sentencing chart[3] and you can calculate that if Aaron had no priors he would be in criminal history category I and have an offense level of 7, which would be a sentence of 4-10 months. That's unpleasant, but it's a far cry from being "likely ... to get 35 years."
In fact, if you look at the sentencing chart, the only way for a first-time offender to have a Guidelines range of 35 years is to be above an offense level of 40. It takes serious work to get there: even a wire fraud of more than $300,000,000 in damages won't get you to that offense level. To get an offense level of 40, you're looking at first degree murder.
Familiarize yourself with the sentencing guidelines and you can see what was actually likely. A judge _could_ depart from the guidelines, but sentences significantly above the guidelines for a first-time offender are all but guaranteed to be struck down on appeal.
To take another example of the difference between maximum and actual sentences: the maximum sentence for murder in many states is death, but not everyone convicted of murder gets the death penalty.
[1] http://www.ussc.gov/Guidelines/2012_Guidelines/
[2] http://www.ussc.gov/Guidelines/2011_Guidelines/Manual_HTML/2...
[3] http://www.ussc.gov/Guidelines/2012_Guidelines/Manual_HTML/5...
Edit: Incidentally, the prosecutor is constitutionally _required_ to inform defendant of the full statutory maximum sentence, even if it's not realistic in a particular case. Failing to do so can be grounds for reversal of a plea or conviction. That doesn't mean the prosecutor has to tell the media, but he/she must tell the defendant.