Depending on what/how many pairings you wanted to start with I would say anywhere from $500-$2,500
I'm still mid-process but here is a breakdown of what I have done:
$550 - animals (1 normal female, 1 male spider, 1 pastel male, 1 pastel 100% het clown female)
$1,200- caging (Animal Plastics PVC caging/thermostats/RBI hides/ceramic water dishes/digital thermometers) (this could be done for much less)
$300 every 6 months - feeders (very rough estimate)
Price for incubator varies greatly depending on if you build your own or buy one (I would budget at least $250 including a good thermostat to run it)
There are other costs, but they are relatively minor.
You could spend far less than I have and still be successful... I'm not a huge fan of racks, so if you use a rack you could easily cut $500 out of my listed caging cost, if not more.