Isn't the way you eat expensive? Does it take a lot of time to prepare?

Those 2 questions come at me all the time.
The answer is generally NO.
Of course there are silly times when a head of cauliflower can cost $7, so you don't buy it til the cost comes down; but even at a pricey $5 a head you can easily get 6-8 servings as a side or if you add it to a curry it could well make 12 servings or more.
Eating a whole plant food way can be as cheap or quick as you want to make it and the two are not always mutually exclusive.
Buying quantity when prices are lower for things like tinned or frozen fruit and veg certainly makes it cheaper, easier & quicker to throw a tasty meal together in minutes.... but the same is true for meat eaters and this way of eating will give more variety, healthier choices and a smaller food budget as long as you keep away from processed foods.
As I keep telling people if you eat processed food it makes little difference whether it has "healthy", "vegan", "low fat", "protein" "vitamin a, b, d, e, k" or any other "in" word on it, it is still processed which means there is little nutritional value in it and all the added "good stuff" is in there so they can call it food not junk.
My friend Gwen is the queen of quick and she is what the Scot's call canny. She buys things with an eye on the budget.
I on the other hand lived so much of my life on the poverty line or below that I can make a meal from nothing and feed a family of 5 with it; but currently I am able to just buy what I want and so I am making the most of that. However, that does not mean I am extravagant, I have a modest budget & stick to it for the main part.
The tricks are to:

• Buy frozen fruits and vegetables, especially when on offer - they are picked fresh & are often cheaper in the long run than fresh.
• If you are happy to soak beans & chickpeas, & really all you need to do is pop them in a bowl with water over night & then rinse add more water & throw in the slow cooker next morning. That evening it ready to use in recipes, just like tinned. If this doesn't sound arduous, then buy them in bulk it is the cheapest way. Other wise look for deals on tins in supermarkets, you can often get them for as little as 89 cents a tin & get at least 4 servings from a tin.
• Lentils again buy in bulk if you are happy to; cheaper but it does add a bit to your cooking time. Red lentils are easiest, cheap & cook in a matter of minutes when added to a dish. Otherwise look for deals on tins of brown or green lentils etc.
• Keep a selection of tins of beans & lentils, veg like tomatoes, corn, green beans etc in your cupboard for really quick additions to salads, soups, stews etc. A chili can be thrown together in minutes with a few tins and some spices.
• Frozen fruit is great, put some out to defrost & throw on your oats or granola in the morning. munch on it straight from the freezer in the summer instead of ice pops, throw in a blender to make instant sorbet.
• Packets of pre-prepared salad mixes, coleslaw veg etc are instant salads. Buy ones without the dressing included as they are cheaper and the dressings are never healthy
• Cheapest salad dressing is a little lemon juice & herbs - fresh really is best. Simplicity is some specialty vinegar; yes that is expensive but a little goes a very long way. I love kraft raspberry dressing, but it is high in sugar so it is a treat, also it has an extraordinary amount of oil, so when I open it I immediately pour all the oil that has risen to the top down the sink. I often cut it with a squeeze of lemon juice to cut the sweetness & use less. Reduced fat Veganaise is great when mayo is needed, again I cut it with lemon or lime juice or a little whole grain mustard and water if I want a thinner dressing. 
• Key things to have in your cupboard are herbs, spices, tamari/braggs liquid aminos, spice mixes like Montreal steak spice or your favourite blend vegan stock cubes, - some  spice mixes & stock cubes have high salt content so keep an eye on that when using. Dried or pre-peeled garlic are useful when you don't have time or inclination to peel & chop fresh.

The most important thing is to make whole plant food eating fit your tastes, your likes, your budget & your schedule. 

Experiment, & Enjoy.