In my country (Brazil) it is quite more expensive to buy a kg of any kind of meat compared to most of vegetables and fruits.
Considering that and assuming it's true in most countries, is it safe to say that vegetarian diet is cheaper than a non-vegetarian? Even considering some vitamin complements that may be necessary?
I hate to say "it depends" but it does.
Firstly, on where you are. However, in my experience of New Zealand, European, and Asian countries it can be and may be in other parts of the world.
Generally it depends a lot on how you approach vegetarianism, it can be very cost effective. Many low-income countries have far lower meat in their diet than developed countries. Many people on student budgets also reduce their meat intake for financial reasons. If you cook mainly with staple foods (rice, corn, beans, potatoes) and buy in bulk it can be much cheaper than many non-vegetarian diets. This doesn't have to be dull, there are plenty of flavours to experiment with and vegetarian dishes from all over the world to try. It doesn't have to be unhealthy either, eating a variety of foods helps to avoid amino acid issues: nuts and legumes are good inexpensive protein sources. If you're a new vegetarian keep an eye on your Iron and B12 levels too.
However, it can be more expensive, particularly for new vegetarians who "substitute" for meat dishes such as with the store-bought soy-based products. As always, cooking dishes from scratch is cheaper. Similarly, I'd caution against the "Organic" vegetarian health foods if you're going vegetarian for financial reasons. There's little evidence that there is a health benefit so and you'll get comparable nutrition for a fraction of the price at a farmer's market or regular supermarket.
It is hard to give an exact answer to this question because it is highly dependent of the location, the actual types of food consumed and possible local culture.
Short answer:
A vegetarian diet should be generally less expensive, if reference omnivore diet includes a decent quality meat. Intuitively, it is generally more expensive to obtain meat at decent quality than obtaining fruits and vegetables at decent quality, as obtaining meat requires more space, more time, more energy, food and water.
Longer answer:
Financial dimension - as expressed in the short answer, meat is generally more expensive than fruits and vegetables. Also, considering possible health benefits, medical expenses are likely to be lower, especially on the long term. This article tries to illustrate the financial benefits of having a vegetarian diet.
Time dimension - in some countries, the "traditional" food is far from being vegetarian friendly. Thus, a vegetarian's life can be harder, especially when not eating diary products, as he/she must either pay higher prices at vegetarian friendly restaurants or cook his/her food. So, it might be more "time-expensive" to be vegetarian in such a context.
I have experience related to this question from two countries: Slovakia and the United Kingdom.
In Slovakia, where the vegetarian and vegan products are scarce, it turned out to be quite significantly cheaper to go vegetarian. Although most of my shopping consisted of regular supermarket groceries, I believe this would still be true if I was regularly buying organic products. Meat, along with cheese, were the most expensive items on my shopping list. After the transition, the only thing comparably expensive are nuts, but I did not buy them as often as meat or cheese.
In the United Kingdom this is (for me) somewhat less true. It all depends on where you buy things and what are your eating habits, of course, but with the plethora of substitutes to choose from and their current "specialty" status, the difference can be much less visible. While living here, I got used to eating a lot of Quorn products, as well as some of the Tesco's own veggie brand. Since living here, I also became vegan and while Alpro milks can be found for reasonable prices, they are still 2-3 times more expensive per litre than regular milk. Vegetables and fruits are also more expensive here (again, it depends where you shop, Aldi and Lidl use to have some really good offers). Another thing that levels these two diets are the ubiquitous "junky" foods like burgers-to-go etc. and these are being sold rather cheaply. Considering my style of living, I would say it is actually slightly more expensive to be vegetarian/vegan here, but the benefits outweigh perceived costs.
To conclude - and I believe this will be true regardless of the country you live in - it all breaks down to what your eating habits are and what requirements you have regarding the freshness, origin and nutritional value of your food.
In my experience, yes. Quite a bit cheaper actually. Very roughly, my transition to vegan was:
Again, that's very rough, and of course may not be the average person's transition (especially if you're into mock meats, fast food, vegan ice creams etc.). A lot of vegan "mock-foods" are currently going through the "speciality" phase, and so naturally you can expect these types of foods to eat up your food budget.
If we're talking about eating as cheaply as possible, then (almost self-evidently) a healthy plant-based diet is cheaper than one which includes meat and other animal products. This is less a statement about economics/budgeting and more a statement about conservation of energy, trophic levels and metabolic heat production.
Some calculations suggest that the US could support an extra 800 million people (or even billions) if the grain that is currently fed to livestock were instead fed to humans (this fact is demonstrative, not prescriptive - no one is suggesting we would immediately stock supermarket shelves with millions of tonnes of corn and soy beans).
Simply put, it's cheaper and more efficient to grow crops and eat them, rather than to grow crops, feed them to animals (who grow muscle mass, produce milk, etc.), and then later, eat the animal products.
I can only speak for the US and southeast Asia and say that the answer is yes and no. The upfront cost of buying fruits and vegetables is much higher than a meat based diet in SE Asia and US. You can easily double or triple your food expense.
However a vegetarian diet decreases the risk of many lifestyle diseases. Getting seriously ill can seriously ruin your budget and eat away all the money you saved by eating meat.
Therefore a vegetarian diet cost more initially but might save you money while a meat based diet is cheaper at first but could cost more through the health risk. This assumes you know how to eat properly while vegetarian.
