Question:

Visa for Iran: 60€ + 2 pictures. Visa extension in Shiraz: 200000 RII (13,5€) + 2 pictures. Fast, 20min (maybe you need to wait half day or one day)

Sleep:
Tehran – Firouzeh: 200000 RII (13.5€) single room with shower + breakfast. Shared toilet. Mr.Mousavi very helpful.
Shiraz – Esteghlal Hotel: 160000 RII (10.5€) single room with toilet and shower.
Yazd - Silk Road Hotel: 50000 RII dorm (3.5€). Toilet and shower shared. Really nice place for meet other travelers.
Esfahan - Amir Kabir Hotel: 60000 RII dorm (4€). Toilet and shower shared. Another place for meet travelers.
Kashan – Ehsan House: 200000 RII (13.5€). Toilet and shower outside. Is one historical house transform into a hotel. Cool place, I stayed there finally.Golestan Inn closed 4months ago. Mosaferkhaneh Guesthouse was full. Sayyah Hotel 250000RII (16,5€) single room. Another place in Ayatollah Kashani St., same price and it looked worst than Sayyah.
Tabriz – Palyan Guesthouse: 70000 RII (4.5€) single room. Toilet and shower shared. Local place, not very clean, but cheap. (Darya Guesthouse was full the dorm. Single room 200000 RII (13.5€))

Public Transport:
Tehran-Kerman overnight train 1st class (bed): 150000 RII (10€). Duration: 15h
Kerman-Shiraz bus: 70000 RII (4.5€). Duration: 8h
Shiraz-Yazd bus: 60000 RII (4€). Duration: 6h
Yazd-Esfahan bus: 40000 RII (2.5€). Duration: 4h
Esfahan-Kashan bus: 27000 RII (1.8€). Duration: 3h
Kashan-Tehran bus: 33000 RII (2.2€). Duration: 3h
Tehran-Tabriz bus: 80000 RII (5.3€). Duration: 8h

Excursions: (Rent one taxi. If you are 2, 3 or 4 people, just divide the price)
Taxi from Kerman to Rayen and Mahan (about 5h in total): 250000 RII (16.5€)
Taxi from Yazd to Tower of Silence and Zoroastrian Fire Temple (about 3h): 100000 RII (6.5€)
Visit from Yazd Meyboy, Chak-Chak and Kharanaj with meal (about 8h): 250000 RII (16.5€)
Taxi from Shiraz to Persepolis and necropolis (about 5h): 250000 RII (16.5€)
Taxi from Kashan to Abyaneh (about 4h): 200000 RII (13.5€)

Others
Taxi from the bus/train station to the hotel (20-40min average): between 10000-30000 RII in almost every city. Always arrange the price before get in the car.
Laundry is quite expensive in general (they charge per piece: around 10000 RII (0.7€) per shock or pants and about 15000 RII (1€) per shirt, trouser or pullover). In some hotels is per kilo (Ej. Amir Kabir, in Esfahan, 30000 RII / 1kg)
Internet: normally 10000 (0.7€) per hour. In some places is cheapier.
Food: In a normal restaurant, full meal with soup/salad + kebab + drink between 30000-60000 RII (2€-4€). In the street, hamburger or pizza between 15000-25000 RII (1€-1.7€)
Tickets: Museums, some mosques and other sights normally between 2000RII-5000RII (0.15-0.35€). Some of them (rarely) between 10000-15000 RII(0.7-1€).
Change: 1€ - 14850-14950 RII depending on the date and on the place.

Regards! I really had a nice time in Iran. The people is unbelievable!!!!!!!!.

Answer:

Check the cheapest Iran tours.

For the hotels in Iran check: Iran hotels.