I for the most part agree with the above comments in that there is no expectation that you would order 5 courses each, so for a basic meal for two, sharing an antipasto, each ordering a primi or a secondo (most likely to share each), then maybe a dessert, is typical.
I would encourage you though to consider finding the opportunity to eat in the classical Italian manner, with a larger group and planning on sitting longer (maybe 2+ hours) Getting a larger group may be difficult, but taking your time is within the reach of a couple.
My preferred meal for two would be one or two Antipasti, I agree they can be the star of the meal, wine of course plus a bottle of mineral water, either still or with gas, Pasta I think is a must, each region has it's specialty (maybe a risotto), then either meat or fish, depending on the region, definitely a contorno, you will get the freshest vegetables, and maybe a dessert if they offer something special (otherwise, a gelato while walking off the meal is my preference). The only Italian tradition I cannot handle though is a coffee after the meal, I cannot drink coffee after noon, but I do like a liquor, a digestive, as a nice cap to meal, especially if there is some local specialty.
As for cost, my experience is that I can get all of that for about the same as I can get a meal for two at Olive Garden, you judge the quality of the food, I think the major cost variation is with the wine. If you do not drink wine, comparative cost can be different, but for what you get a glass of wine in the US, you can get a large carafe or bottle in Italy