How much money did I save by making a sandwich for dinner?

I recently started making sandwiches for dinner instead of eating out. As I was preparing my sandwich tonight, I wondered how much money I was really saving. So I decided to look at the cost per serving for all of the ingredients in my sandwich. By serving I mean the measure of how much I actually eat rather than what's defined on the nutrition label. For the cost calculations, I'm rounding to the nearest tenths.

Cost of ingredients

1. Arnold Whole Grain Bread

Price: $4.49

Total slices: 16

The nutrition label defines one slice as a serving. Like most people, I eat two slices.

Cost per serving of bread = (4.49 / 16) * 2 = 0.56

2. Natural Choice Smoked Deli Ham

Price: $5.50

Total slices: 16

I use about four slices for each sandwich. 

Cost per serving of ham = (5.50 / 16) * 4 = 1.38

3. Applegate Sliced Provolone Cheese

Price: $5.99

Total slices: 12

I use two slices. 

Cost per serving of cheese = (5.99 / 12) * 2 = 1.00

4. Hellmanns Real Mayonnaise

Price: $4.79

Total amount: 30 tbsp

I use about one table spoon. 

Cost per serving of mayonnaise = (4.79 / 30) = 0.16

5. Romaine Lettuce

Price: $2.99

Total amount: ???

I just finished up this lettuce and I've had it for quite a while. I think it's been used for about 12 - 13 sandwiches. Lets say it's 12. 

Cost per serving of lettuce = (2.99 / 12) = 0.25

Total cost of my sandwich

Total cost = (0.56 + 1.38 + 1.00 + 0.16 + 0.25) = $3.35

Holy shit. 

How much do I typically spend on dinner when I'm eating out? $10 - $12. Lets say $11. That means I just saved $7.65 tonight!

If I ate out every night for a month, I'd spend $330 on dinner alone for that month. If I ate a sandwich (with equivalent cost to this one) every night, it would only cost me $100.5 a month. So in theory (I say theory because I cannot eat sandwiches every single day for a month), if I ate these sandwiches for a month instead of eating out, I'd save more than 200 dollars!