The most common question I had after coming back from Japan was “are things there expensive?”, “how much bread costs?", “is rice cheaper there?”. I had exactly the same questions before I went there. Now, That I’ve seen it with my own eyes (and made extensive notes) I can share my experience with all of you and answer those questions!
Here are some prices of “basic” cooking ingredients. But first, I would like to point out some things:

• the data in here is just something I collected during my stay. It's not average and almost all of them are from Tobu supermarket, nearby to where I used to live. 

• all prices contain 8% tax (most of supermarkets have prices without VAT, which is added at the very end. I added it, so it would be easier to count and compare).

• since I had to multiply prices to get the price with tax, we have those ugly endings of decimal place. I left them (even though something like 0,60 of yen doesn't exist) because money calculation usually (at last in my country) operates with approximation to 4 decimal places, and it kind of makes a difference if it's 228,96 or 228,06. Normally prices without tax would be added up and then the tax would be counted.  I simply have no idea which method of rounding they use, so I'm leaving it this way to be more precise.

• prices are calculated based on exchange rate for 16th of October 2015.
  100 yen= 0,7375 €
  100 yen = 0,8380 $
  100 yen = 0,5421 £ 

Basics

Product	¥	€	$	£
eggs x6	183,60	1,35	1,54	1,00
eggs x10	258,12	1,90	2,16	1,40
milk 1l	182,52	1,35	1,53	0,99
toast bread (8 slices)	124,20	0,92	1,04	0,67
butter	214,92	1,59	1,80	1,17
salt 1kg	136,08	1,00	1,14	0,74
sugar 1kg	194,40	1,43	1,63	1,05
vegetable  frying oil 900g	388,80	2,87	3,26	2,11
grated cheese 200g	228,96	1,69	1,92	1,24
pasta (noodles)	95,04	0,70	0,80	0,52
mayonnaise	203,04	1,50	1,70	1,10
ketchup 500g	152,28	1,12	1,28	0,83
strawberry jam 160g	235,44	1,74	1,97	1,28
corn flakes	204,12	1,51	1,71	1,11
muesli (granola)	429,84	3,17	3,60	2,33
crunch cereals with fruits 280g	300,24	2,21	2,52	1,63
pudding 3x70g	106,92	0,79	0,90	0,58
cream cheese x3	139,32	1,03	1,17	0,76
vegetable salad	103,68	0,76	0,87	0,56
frozen rice with vegetables 140g	264,60	1,95	2,22	1,43
frozen fries 140g	140,40	1,04	1,18	0,76

Fruits and Vegetables

Product	¥	€	$	£
pineapple	321,84	2,37	2,70	1,74
carrots x3	213,84	1,58	1,79	1,16
bananas x5	213,84	1,58	1,79	1,16
kiwi x3	213,84	1,58	1,79	1,16
cabbage 150g	108,00	0,80	0,91	0,59
muschrooms 100g	213,84	1,58	1,79	1,16
garlic x1	278,64	2,05	2,34	1,51
watermelon 1/6	537,84	3,97	4,51	2,92
onion x1	73,44	0,54	0,62	0,40
sprouts 250g	30,24	0,22	0,25	0,16
japanese peach x1	216,00	1,59	1,81	1,17
apple x1	213,84	1,58	1,79	1,16
lemon x2	170,64	1,26	1,43	0,93

Meat and fish

Product	¥	€	$	£
bacon (raw) 8 slices	192,24	1,42	1,61	1,042133
mini sausages 152g	297	2,19	2,49	1,610037
pork chop 131g	301,32	2,22	2,53	1,633456
beef bacon 145g	250,56	1,85	2,10	1,358286
tuna tin 70g x3	430,92	3,18	3,61	2,336017
ham 12 slices	289,44	2,13	2,43	1,569054
raw salmon (pieces)	303,48	2,24	2,54	1,645165

Drinks

Product	¥	€	$	£
orange juice 1l	152	1,12	1,27	0,823992
Coca Cola 500 ml	96,12	0,71	0,81	0,521067
water 550ml	108	0,80	0,91	0,585468
green tea 525 ml	129	0,95	1,08	0,699309
Royal Milk tea500ml	101,52	0,75	0,85	0,55034
beer 350ml	186,84	1,38	1,57	1,01286

Japanese cuisine

Product	¥	€	$	£
rice 5 kg	1922,4	14,18	16,11	10,42133
soy sauce 1l	159,84	1,18	1,34	0,866493
rice vinegar	258,12	1,90	2,16	1,399269
dashi 140g	322,92	2,38	2,71	1,750549
shiro miso 500g	410,4	3,03	3,44	2,224778
udon	214,92	1,59	1,80	1,165081
okonomiyaki sauce	235,44	1,74	1,97	1,27632

Conclusion: 

What hit me first in Tokyo, was how expensive fruits and vegetables are and that the price is fixed to a piece, not weight. It was really hard to get used to the fact that an apple costs over 200 yen, while in my country I pay at most 80 yen for 1 kg. Another surprise was the price of rice- over 1900 yen and no real alternative for that one. Just saying- I pay around 100 yen for a kilo (not the same type, but it’s still rice). Good news: fish are cheap (once during promotion in supermarket I managed to buy salmon fillet for 100 yen!) and other Japanese specials like soy sauce. As obvious as it sounds- if you don’t want to overpay, eat what locals eat. The question is, how to use all those unfamiliar things? Well, that’s what my Japanese Cookbook is for ;)

You have anything to add? You know a place where to buy things cheaper or you wonder how much something costs? Feel free to comment!