It's a common misconception that a vegan diet is expensive. Sure. If you choose the vegan option in a restaurant it might be more expensive because there's less demand. Vegan restaurants may be expensive because it's still quite a niche market. Fake meat products can be expensive because again they are affected by supply and demand. Vegan cheese is usually expensive but I'll be honest with you, personally I think vegan cheese is vile, I don't buy it but I also don't miss cheese.
However, eating an every day vegan diet really isn't expensive.
Most vegans live primarily on fruit, vegetables, rice, beans, lentils etc. You can buy fruit and veg cheaply, if you go for seasonal ones, some stores do less than perfect vegetables and you can buy vegetables in bulk when you find them at a low price and freeze them.
Buying vegetables, grains etc (you can buy them tinned and dried) is cheaper than buying joints of meat.
You could make, for example a cottage pie, using a tin of chickpeas, some lentils and seasonal veg. Chuck in a tin of budget brand tomatoes and you've got a cheap meal.
You could buy a load of cheap veg, if you shop at the right time you might even find it reduced, blitz it up into a soup, and you've got lunch for a week.
You could make a bolognese using tinned tomatoes, lentils and some cheap veg. Which I'm entirely sure is cheaper than a packet of mince.
You can even buy plant milk in Aldi and Lidl.
You might be surprised at how many things you can buy in even the cheapest supermarkets that are accidentally vegan.
Being vegan is like most other things, it can be as cheap or expensive as you make it.
If you go for the premium brands of milks, yoghurts etc it will of course cost you more, but if you shop wisely, plan your meals, you will most likely see your grocery bill decreasing.