Youre right, The 2 port vaults are $176 which is almost double your budget. I figured you could find a used one for cheaper, but I just looked around and you cannot :(
You can check out ODROID. The ARM version for $83 and a x86 version for $129. You can play around with specs and models and get those numbers down lower. Pretty large community playing with them, BSD probably can support them or at least the info is most likely in a forum somewhere.
thank you for that clarification!