Looking at it's history, it was for sale for 10,000 GBP for several years and then 18,500 USD. Finally, 1495 USD for about a year before it was finally dropped.
There are several companies, including Norton, offering smart firewalls. Though I'm not sure the term has really caught on. I use Norton and I've always just called it a firewall.
According to GoDaddy appraisal, "Valuable keywords: smart and firewall are high value keywords with an average sale price of $2534 and $1929."
Reasonable, I'd say low to mid $xxxx. $49,995 is more a 'unicorn' price.