Booking accommodation with a kitchen looks like an obvious saving against restaurant prices. The saving is real but consistently smaller than travellers estimate, for reasons that are structural.
Staples are bought in full units
Cooking anything requires oil, salt, pepper, a condiment and something to cook in. Those are bought as whole containers and mostly abandoned at the end of the stay.
That fixed cost is spread across however many meals get cooked. Over a week it is modest; over a long weekend it can approach the price of the meals it replaced.
The same applies to quantities. Vegetables and meat are sold in portions sized for households, and a couple cooking twice discards a good share of what they bought.
Holiday kitchens are minimally equipped
A rental kitchen usually has one usable pan, a blunt knife and a hob with an unfamiliar control layout. Cooking anything ambitious is slower and less satisfying than at home.
Missing equipment forces substitution or purchase. Travellers regularly buy a knife or a corkscrew that stays behind, which adds to the fixed cost again.
The result is that self-catering trends toward simple food. Simple food is exactly what is cheapest to buy ready-made, which narrows the gap further.
Shopping consumes trip time
Finding a supermarket, working out an unfamiliar layout and queuing takes an hour or more on the first attempt. That hour is drawn from a limited supply of days.
Without a car, shopping is constrained by what can be carried back. That means more frequent, smaller trips at higher unit prices from convenience shops.
Opening hours in many countries are shorter than travellers expect, particularly on Sundays and holidays. A missed window sends everyone to a restaurant anyway.
Where the saving is genuinely large
Breakfast is the clearest win. Hotel breakfast is priced well above its cost, and coffee, bread and fruit from a shop replace it for very little.
Families gain the most because portion sizes finally match a household unit. The fixed pantry cost is spread across many more meals.
Long stays shift the arithmetic decisively. Beyond about a week, the staples are amortised and the daily cost approaches what it would be at home.
The part that is not about money
Eating out is often the point of the destination rather than an expense to minimise. Cooking in a rental in a city known for its food trades the experience for a small saving.
Dietary requirements change the balance, and a kitchen removes daily negotiation over ingredients. Travelling with young children has a similar effect.
The useful framing is control rather than cost. A kitchen buys flexibility over timing and content, and the saving is a secondary benefit.