I hate to say it but there are lots of other costs to consider:
Initial vaccination costs and checks. Not hugely expensive but it can be a lot once you've paid for everything else.
Minor vet bills that fall under your insurance excess - in five years, we've had to pay for 2 x cut paws, a stomach upset, an injection to make him sick after he ate something he shouldn't, medication for a lump on his face and antibiotics for a bite. Our excess is £120 but all those vet visits came to between £40-90 each.
You'll also need to pay the cost of a spay/neuter as they won't be covered by insurance.
The cost of flea/worm/tick treatment every three months - you can often get a payment plan from the vets but it's still an added cost.
Teeth cleaning/removal - this often doesn't come under insurance and will need to be paid for out of pocket. It can range from around £200-900 depending on the breed and how much work needs doing.
Puppy classes - not essential but strongly recommended if you've never trained a dog before. Ours was £10 a session but that was 5 years ago, so it's probably gone up a bit since then.
The cost of a dog-walker/sitter if you want to go out for the day and can't take the dog. Also the cost of kennels/boarding if you want a holiday where you can't take the dogs - remember most holiday accommodation won't allow the dogs to be left, so they'll need to come with you everywhere.
Replacement leads, collars and beds when they outgrow them, or they get really manky, or the dog eats them...
Chews and treats for training and to help with teething etc. Most adult dogs still like to chew and will want something available to them most days.
Things to puppy-proof your house - baby gates, blankets for beds and sofas, doggy cleaning products for when they inevitably pee on the floor, child locks for cupboards and bins...
I'm sure there's even more - they're not cheap pets by any stretch of the imagination! Yes, there are some things you can "buy cheap" and some things won't be necessary depending on your lifestyle and experience, but they're all things to consider. I find that most months there's something I have to buy that I never budgeted for!