The time of year that you travel will have effect on the amount of money you spend as costs vary depending on the seasons.
Summer in Italy is the most expensive and busiest time. Prices for everything are considerable higher.
I find that Summer is not the ideal time for me to travel to Italy. There are too many crowds everywhere with long lines to get into any sights, venues, churches, basilicas, everything.
Accommodation, food and even transport is higher than other times of the year. I know for many of you that is the only time you are able to travel so the extra cost is a consideration in your decision.
Summer is a beautiful time, as is anytime in Italy it is gorgeous, you just need to be prepared to pay more and wait longer for everything.