Yes, that is so true, its a lot of money for what you are actually getting. However, it depends on if you need a vapor phase soldering solution. Then the lower cost options are limited to maybe two.
My thoughts, were to control the power with phase control (say 0 to 100%), and PWM the fans (5 to 100%), either have two halogen heater tubes (500W each) or a silicon heater mat and have a touch screen for the control.
A simple method to edit / create the profile in steps. Each step would endpoint with temperature or time and be either cooling or heating, with a percentage value for power (Heat or cool), when the step endpoint is reached (time or temp) it moves to the next step.
That way the control could be pretty good, with multiple steps I think you could achieve a good temperature profile.
And perhaps with a keep warm function, maybe to just keep the fluid above ambient, for faster throughput.
Maybe some sort of better lid / cooling design to try to minimise the loss of fluid.
Just thoughts really.
Maybe convert an ultrasonic tank/bath unit. They can be about the right size and have lids and picked up fairly cheap.
I am surprised that their is not a low cost, maybe smaller, version available aimed purely at hobbyist. I think it would really work. Could be fairly small really.
Interesting. I did look around to see if stainless tanks are available off the shelf that may suit, but not found much.
Interesting, what's available:
https://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2332490.m570.l1313&_nkw=untrasonic+tank&_sacat=0