Ok so we have 2 large dogs, but will work on the basis of one.
£10 for large sack of complete dog food (would last one large dog 4 weeks). Also about £5 per month on treats.
I strongly advise pet insurance! We saved nearly £3K in the first 2 years of having ours because we had insurance (one broke it's leg running, one got attacked by another dog and needed 41 stitches!). Pet insurance is about £250 per year.
Vaccinations and worming- about £25 per dog per year
Initial outlay of £20 quid or so on a collar, bowls, lead and ID tags.
Don't need a 'bed' as such - old duvet or blankets in a cardboard box is OK.
I have 2 small dogs both are puppies though so the prices might be different when there adults.
Food - dry food one bag lasts a month which is £7 wet food about £12 a month treats prob £5 a month
Flea treatments & wormers - works out at £5 a month
Insurance - mine are still under their free insurance but the quotes i have are £8 a month each. But it goes up when there older to about £20/30 a month each!!
Groomers - Ive learnt how to do it myself but before I was taking my fluffy dog to the groomers once a month and it was £12 each time (it goes up when there fully grown) so thats worth taking into consideration.
Vaccines - initial ones are £40 each then £20 a year after that neutering - starts at £60 for boys and £100 for girls, goes higher the heavier they are but is cheaper if your on benefits.
Initial outlay - bloody fourtne in Pets at Home!!! I cant even count how much, crates, beds, leads, collers, id tags, grooming kit, bowls, toys the list goes on though in sure you could do it a lot cheaper
So prob about £30 a month each, but it can prob be done a bit cheaper. If you fed them only dry food etc.
One GSD is epileptic and so needs completely additive-free food - currently running at about £80 per month but looking to reduce that atm by feeding raw or an additive free complete food. Add to that the price of his medication (although I don't pay for his meds as he's a long term foster dog so the rescue does).
The other GSD and the Lab X are on kibble plus Naturediet - food bill approx £60 per month. Pet insurance for these two is just under £30 per month - it's the "extra" insurance which doesn't stop paying out after 12 months have passed but is tailored not to include anything such as kennelling fees if I'm in hospital, travel insurance or advertising if lost (I'm a rescuer so can arrange kennelling and advertising myself), nor does it include 3rd party insurance - purely vet fees alone.
Treats - about £20 per month.
Mine don't have anything but old duvets/blankets inside plastic beds (yet the plastic beds alone cost £20 plus each!) because one of the Sheps rips up bedding and besides, they sleep on the sofas most of the time!
Flea treatment/wormer - again more expensive for GSD1, about £20 per month. Vax - between £25 to £40 per year each. Sundries - collars, leads, endless tennis balls, haltis - bloody fortune as and when.
Looking at it all, I now know why I'm often found to be moaning that money doesn't go far these days!