Having worked in this industry for twenty years, I can tell you that quality always matters more than price.

"I can tell you (that)" 是固定表达，用于加强后续陈述的分量和可信度，can 在此不是能力"能告诉"，而是强调说话人确信程度的语用标记，常配合个人经验或权威身份使用。