Good day Henderson,
Thank you for reaching out to us. PlusSpec has always been available for Mac.
Our plans and information can be accessed here https://plusspec.com/plans-pricing-1/?currency=AUD&render_wpcs=1
The price you quoted as only an introductory price we had four years ago. However we have other economical options available in the above link.
I am happy to assist if you have any further questions.