Baymard
Baymard is a UX research subscription rather than a pure audit tool: the value is a large library of evidence-based guidelines drawn from its own usability studies, plus a site scanner that checks your pages against them. Higher tiers add industry-specific research, competitor comparison and expert consultations. Every paid plan is billed annually, so the monthly figures are an annual commitment in disguise.
Information
$200/mo Foundation; $350/mo Expansion; from $700/mo Custom - all billed annually only ($2,400 / $4,200 / $8,400+ per year)
Other Info
Free
Yes