Keşif bedeli yüksek; öte yandan yüklenici güvenilir.

In Turkish, present-tense sentences with a noun or adjective predicate often use a zero copula in the 3rd person.

So:

• Keşif bedeli yüksek = The estimated cost is high
• Yüklenici güvenilir = The contractor is reliable

Turkish does not need a separate verb like is here. In more formal or emphatic language, you may sometimes see -dir added, as in yüksektir.

Keşif bedeli is a set expression, especially common in technical, construction, or procurement contexts.

A rough breakdown is:

• keşif = inspection, survey, estimate, or cost calculation, depending on context
• bedel = price, cost, amount

Together, keşif bedeli usually means something like:

• estimated cost
• estimated price
• appraised amount

The most natural English wording depends on the context.

This is because keşif bedeli is a Turkish noun compound.

In many Turkish noun compounds, the second noun takes a 3rd-person possessive ending:

• araba kapısı = car door
• proje maliyeti = project cost
• keşif bedeli = estimate/appraisal cost

So bedel becomes bedeli.

This does not mean someone personally possesses it. It is just how this kind of compound is formed in Turkish.

That is a very common point of confusion.

In Turkish:

• Attributive adjectives come before the noun:
  yüksek keşif bedeli = a high estimated cost
• Predicate adjectives come after the subject:
  keşif bedeli yüksek = the estimated cost is high

So in your sentence, yüksek is not directly modifying the noun inside the noun phrase. It is the main predicate of the clause.

Öte yandan is a linking expression meaning:

• on the other hand
• on the other side of the matter
• sometimes besides or meanwhile, depending on context

In this sentence, it introduces a contrasting consideration:

• one fact is negative or problematic
• another fact is positive or balancing

It is a little more formal and discourse-like than a simple ama or fakat.

Yes, in many contexts you could express a similar contrast with those words, but the nuance changes.

• ama = very common, conversational, simple but
• fakat / ancak = more formal but / however
• öte yandan = on the other hand, often used when weighing two sides

So:

• Keşif bedeli yüksek ama yüklenici güvenilir.
  This sounds more straightforward and conversational.

• Keşif bedeli yüksek; öte yandan yüklenici güvenilir.
  This sounds more balanced, written, and analytical.

In everyday literal terms, yüklenici comes from a verb related to undertaking or taking on something. But in real-world usage, especially in legal, business, or construction Turkish, yüklenici usually means:

• contractor
• supplier
• the party undertaking the work

So in this sentence, it most likely refers to the contractor or company responsible for carrying out the project.

In this sentence, you should treat güvenilir as an adjective/predicate adjective meaning:

• reliable
• trustworthy

Historically and grammatically, it is related to a verbal form from güvenmek (to trust), and its structure can be analyzed as something like trusted / one can trust. But for learners, the most useful thing is:

• yüklenici güvenilir = the contractor is reliable

So here it functions like an adjective.

No. They are related, but not the same.

• güvenilir = reliable, trustworthy
  Used for a person, company, source, system, etc.
• güvenli = safe, secure
  Used for places, situations, systems, conditions

Examples:

• Bu satıcı güvenilir. = This seller is reliable.
• Bu bölge güvenli. = This area is safe.

So in your sentence, güvenilir is the correct choice because the topic is whether the contractor can be trusted.

The semicolon joins two closely related independent clauses:

• Keşif bedeli yüksek
• öte yandan yüklenici güvenilir

It signals a stronger pause than a comma, but the ideas are still closely connected. This is quite natural in formal or written Turkish, especially when presenting two sides of an issue.

You could also write it as two separate sentences, or rewrite it with a conjunction such as ama or ancak.

Turkish usually does not use articles like the and a/an in the same way English does.

Whether a noun is understood as definite or indefinite often comes from:

• context
• word order
• whether bir is used
• the overall situation

So keşif bedeli and yüklenici can naturally be translated as the estimated cost and the contractor if the context makes them specific.

It sounds somewhat formal or written, mainly because of:

• öte yandan
• the semicolon
• the compact, report-like style

A more conversational version might be:

• Keşif bedeli yüksek ama yüklenici güvenilir.

Both are correct, but your original sentence sounds more like written evaluation, reporting, or professional discussion.