Monthly Income and Prices for 1 modius Wheat in the 1st century AD:

Job
Denari / month
Secretary
15
Lecturer
12
Messenger
9
Haruspex (fortune teller)
10
Legionary Soldier (Private)
20
Praetorian (guard in Rome)
60
Legionary Soldier (Centurion)
~300

Location
Price / As
Rome
up to 32
provincial Italy
16
Africa
9 - 16
Asia minor
8 - 16
Palestine
10 - 12
Egypt (bread basket)
7 - 9

Other Prices:

1st century AD
Price
1 modius wheat
see above and right
1 loaf bread
1 dupondius
(=2 As ; in Rome)
1 sextarius wine
(~0.5 liter)
1 - 5 as
1 sextarius fine wine
up to 30 as
a bath at a public bath
1/4 as
1 tunika (clothing)
15 sestertii
1 donkey
500 sestertii
1 general slave
2000 sestertii = 500 denarii (up to 1500)
1 pretty female slave
2000 - 6000 denarii
1 morgan land
1000 sestertii = 250 denarii

Average price in As for
1 Modius wheat:
(values of Rome and Italy
derived from Egypt)

 
Rome
Italy
Egypt
18BC-14AD
16
8
4
14 - 98
32
16
8
98 - 192
40
20
10
193 - 260
68
34
17

In the Republic (c.200-150 BC) we find records of the pay for a legionary soldier set at 3 asses per day and wheat sold for 4 asses per modius. This would allow a soldier to buy enough bread for a year with about two month's pay. The revaluation of the denarius from 10 to 16 asses in 141 BC raised the legionary pay to 5 asses a day and the price of wheat to a bit over 6 asses per modius. By the time of Caesar, a legionary made 10 asses a day but wheat cost 12 asses a modius. Allowing for local variations all of these prices remained somewhat proportionate to the wages. During the early Empire a modius would sell for two denarii in Rome but could be had for half that price in the rural parts of Italy and only 8 asses (half a denarius) in the breadbasket of Egypt. Baked bread sold for a dupondius a loaf in the expensive cities like Rome and Pompeii and half that (one as) in more rural towns. By this time the legionary was earning nearly a denarius a day but the Praetorian Guard (at Rome) were paid more partially for their honored position and partly to offset the expense of living in the City. Comparing today's prices for bread at the supermarket might suggest an as was worth a bit over a dollar US placing the denarius at about $20.

http://www.the-colosseum.net/history/monete_en.htm