Hi, I am German, living and working in Tehran since 2007 and am planning to bring my TT600R to Iran in August as this is a wonderful country for bike-travelling!
I have checked the regulations with the Iranian Customs office in Tehran.
A Carnet de Passage is officially required for every temporary import of a foreign vehicle to Iran.
(In addition to this, there seems to be some strange obligation to engage an official tour guide for each traveller entering the country with a vehicle. This seems to be relatively new and still needs to be confirmed. It's possible that a pre-entry registration with the Touring & Automobile Club of Iran might be sufficient. I will be checking on this.)
I know, that this is Iran and that Iran is located in this region of the world, so, there is always 100s of ways around the law!
And this always costs some money to be paid to the friends of the friends of the guys in charge - and then to others that might object and-so-on.
Nobody will be able to do the No-CdP-Service without such payments (as stated above: approx. 250 EURO). Plus this by-pass of the law seems to be limited to 2 weeks...
If you only do transit (to/from Pakistan/Turkmenistan) or short trip into the country and back AND you are lucky to not run into some very strict representative of the authorities you might get off with less official paperwork before departure and save a few EUROs...
But, if not, this might end much more expensive...
Thus, besides the risk of incertainty, I do not really see a relevant financial benefit deviating from the official way with a Carnet de Passage.
And don't be mistaken:
Iran is a country with a rather well interconnected and organized administration. It is not wise to bother with them, and if you run into trouble things get intransparent, incomprehensible for foreigners and extremely time consuming quite quickly! Plus costs for fines etc...


Why would one want to risk the official, legal and smooth entry into this country half way round the world from Europe, just to save 50 EUROs or so?
The ADAC of Germany charges me 195 EUROs for the CdP (plus 3000 EUR bank deposit), valid for 1 year with the possibility of extension.
So, I will do it this way and am nervously waiting for the day of departure...!

Cheers,
Daniel