La tarifa de datos es barata.

Because tarifa is a feminine noun in Spanish, so it takes the feminine singular article la.

• la tarifa = the rate / the plan
• feminine singular nouns usually pair with la

You generally have to learn the gender of each noun as part of the word.

In this sentence, tarifa means something like rate, plan, or pricing. With de datos, it usually refers to a mobile data plan or data rate.

So la tarifa de datos can mean:

• the data plan
• the data rate
• the mobile data tariff

In Spain, tarifa is very common for phone, internet, and transport pricing.

Spanish often expresses this kind of idea with noun + de + noun.

So:

• tarifa de datos = literally rate/plan of data
• natural English translation = data plan or data rate

This de structure is extremely common in Spanish:

• tarjeta de crédito = credit card
• gafas de sol = sunglasses
• centro de salud = health centre

Because Spanish normally uses datos in the plural when talking about mobile data or digital data in general.

So:

• datos móviles = mobile data
• tarifa de datos = data plan

Even though English often uses data as an uncountable mass noun, Spanish frequently uses datos as a plural noun.

Because barata describes a general characteristic of the data plan, not a temporary condition.

• es barata = it is cheap as a quality or defining feature
• está barata would suggest something more temporary, like it’s cheap right now

With price, cost, and usual characteristics, ser is the normal choice.

Because adjectives in Spanish usually agree in gender and number with the noun they describe.

Here the noun is:

• la tarifa → feminine singular

So the adjective must also be feminine singular:

• barata

Compare:

• el plan es barato
• la tarifa es barata
• los planes son baratos
• las tarifas son baratas

Not always. Barata means cheap / inexpensive, but the tone can vary depending on context.

• barato/barata is very common and often neutral
• económico/económica can sound a bit more positive or formal, like affordable or economical

So you could also say:

• La tarifa de datos es económica.

Both are correct, but barata is very natural in everyday speech.

Yes, if the context is already clear.

• La tarifa es barata. = The plan/rate is cheap.
• La tarifa de datos es barata. = specifically The data plan is cheap.

Including de datos makes the meaning more precise.

Because this sentence uses a linking verb structure:

• La tarifa de datos = subject
• es = linking verb
• barata = predicate adjective

So the pattern is: noun + ser + adjective

This is very normal in Spanish:

• El coche es nuevo.
• La casa es grande.
• La tarifa de datos es barata.

If the adjective were placed directly next to the noun, the structure would be different:

• la barata tarifa de datos is technically possible, but sounds much less natural here

In standard Peninsular Spanish, roughly:

la ta-REE-fa de DA-tos es ba-RA-ta

A more detailed approximation:

• la
• ta-RI-fa
• de
• DA-tos
• es
• ba-RA-ta

A Spain-specific pronunciation point:

• In much of Spain, z and soft c are pronounced like the th in thin
• But here there is no z or soft c, so nothing unusual happens

Also, the stress falls on:

• ta in tarifa? No — actually ri: ta-RI-fa
• da in datos: DA-tos
• ra in barata: ba-RA-ta

Yes. Tarifa is a flexible word that can refer to different kinds of rates, fares, or pricing structures depending on context.

For example:

• tarifa de datos = data plan
• tarifa eléctrica = electricity rate
• tarifa plana = flat rate
• tarifa de taxi = taxi fare/rate

So the exact translation depends on what follows tarifa and on the situation.