One.) .most definitely can get a decent one in that price range. elegoo mars 2 pro $245 , anycubic photon mono se $340 Those are what I would call small format printers. Personally I would spend a little bit more and go with the elegoo saturn $500 As it is the lowest cost medium format resin printer I've found and it has great reviews.
Two) .you can save your unused resin by using a filter and straining them back into the bottles. The printers I use came with a vat cover that clips over the resin vat when not in use so I just bought spare vats and have a cabinet I keep my covered resin vats in but they can be left on the printer.
Three) .A 1Kg filament Spool of PLA, ABS and PETG sells for $20 and the price of resin is $15-$45 for 500ml and $28-$80 for 1 liter. However, resin printers have many other associated costs that can’t be ignored, such as replacing the resin tank, for film, buying large quantities of isopropyl alcohol, as well as protective equipment(respirator, nitrilegloves, papertowels, and a UV curing lamp.( I recomend getting a wash cure station, like this wash cure or if you go with a medium format printer then this wash cure plus
Four) .the quality is amazing, super crisp and clear with super fine detail but you pay for it with all of the consumables you need to get (iso, gloves, respirator etc)
Five) . People will say no but you want to make sure you use a respirator that filters organic matter and fine particulates and gloves when working with ANY KIND of liquid resin, there are bio compatible resins however they are only safe once cured and the liquid resin is still toxic. I know first hand how deadly resin exposure can be(my dad passed away this year from a long battle with an uncurable lung disease developed after working in additave manufacturing for 20yrs ) Are we talking no ventilation or very little? You could always hook up an extractor fan and some ducting for when in use, but many of the printers include an active carbon air filter so you really only need to worry if the printers open.
In all it is more expensive, but you get higher detail and the printers tend to print alot faster.