What phrase indicates a barrier that customers face?

The phrase that indicates a barrier that customers face is "But...". This word often serves to signal a contrast or an obstacle in a given situation. When used in a discussion, it typically introduces a complication or a challenge that counters previous statements. For instance, if a product has many benefits but also comes with a significant drawback, saying "But..." highlights that drawback as a barrier that customers might encounter.

The other phrases do not typically serve the same function. "However..." can also indicate contrast or an exception, but it is often used in a more formal context and may not immediately convey the idea of a barrier. "Although..." introduces a condition or limitation but is more focused on framing alternatives rather than emphasizing a drawback. "In conclusion..." signifies a summary or wrap-up, which does not pertain to identifying barriers customers face. Therefore, "But..." is the most effective choice for illustrating obstacles in customer experiences.