Long story short, my route was from Osaka Kansai Airport to Hiroshima (Iwakuni if we’re being exact) and back again with many stops along the way. I was there for 14 full days and left the morning of the 15th. I’ll post the prices in yen so it’s more precise, you call all exchange that to your local currency if you wish.

TRANSPORT: 21,820円 total (about 1450円/day)
As for passes, I did have a ‘Visit Hiroshima Tourist Pass’ (small version 1000円, lasts three days). If you’re doing Hiroshima / Miyajima as a day trip maybe the one day-pass would be a better option, but I was there for a longer time.
I also used the discount ferry for foreigners going from Kansai Airport to Kobe Airport, from there taking the Port Liner into Kobe, which proved cheaper than if I’d taken the local train through Osaka.

ACCOMMODATION: 38,800円 total, 14 nights (about 2600円/night)
People sometimes run the other way when they hear the words ‘hostel’ or ‘dormitory’, but hostels in Japan are very clean and it’s a great way to get to know other travellers, especially if you’re going solo. Many hostels are in old houses and have tatami too, if you’re looking for something more traditional.
I asked for the dorm in all cases but I only actually ended up sharing a room in Osaka and Hiroshima, the other hostels didn’t have any other guests so I had the room to myself. In most rooms there was a separation of some kind (may it be a curtain, half a wall, a more pod-like bed, etc.) so I wouldn’t see the other people sleeping in the same room from my bed.

FOOD: 17,990円 total (about 1200円/day)
I don’t really stick to mealtimes so sometimes I’d buy two big bentos in the morning and eat a bit whenever I’m hungry during the day, buying extra snacks along the way.
As for drinks, I don’t drink beer so that isn’t included. I usually had a vending machine drink every day at around 130円 but when it started to get hotter in July and I needed more to drink I bought a big bottle from the supermarket or konbini and carried it around with me all day. I think next time I’m just going to buy a big bottle of water on my first day and refill it every morning with water from the hostel, it’ll definitely save me quite a bit of money even if it means missing out on all the different vending machine flavours.

SIGHTSEEING: 11,770円 total (about 850円/day)
Here I’ve included of course entrance fees to museums and gardens, as well as things like renting a bike, entrance to a Kagura show in Hiroshima (1000円), a boat ride in Kurashiki (500円), etc.
Look out for combination tickets to places within cities, for example the combination ticket for Himeji Castle + Koko-en, or the one that includes Kintai-kyo + ropeway + castle in Iwakuni (plus a discount). When in Tokyo on my first trip I had the Grutt Pass which was very very useful. I think it costs 2500 yen if I remember correctly but it paid off right away thanks to my obsessive museum-visiting.
As a side note, (small) lockers at stations added up to 900円 in total after 3 uses, I’ve also included locker use in this category since they were directly related to my sightseeing. Once I used the locker of a museum (Hiroshima Prefectural Museum of Folklore in Fukuyama, for 100円 and they return the coin after use) instead of using a locker at the station that would’ve cost 700円 instead —there were no small ones left. It’s the little things like this that really add up in the end.

SHOPPING: 10,830円 total (about 730円/day)
What took most of the money from this category were the goshuin temple stamps I got, at 300円 each one (so 1800円 in total). The stamp book cost me 1000円 at Engyo-ji of Mt.Shosha. Other examples of things I bought are a couple of books at Hiroshima Peace Museum (2550円 total), two tenugui that I used as towels and are now good souvenirs (856円 the two), packet of 8 batteries (600円), tabi socks (100円) and a rice scoop at Miyajima (360円), between others.
I bought a very expensive umbrella at Sannomiya Station in Kobe thinking that it would be raining once I left the train in Himeji but I only used it once during my whole trip and wished I’d waited until I found a cheaper one at any konbini or 100 yen store.

Well, there you have it.
TOTAL OF EVERYTHING: 100,610円 (plane not included, since it depends on where you’re coming from). That means about 6700円 a day including accommodation!