If I was going to do a minitub, at least $800.
Is it easy, not so bad. However, you need the equipment to do it and there are some tricks to getting it done. Overlapped or buttwelded tub patch? Tub on side or on top of frame? With floor patches, then it's less than a cleaner, no floor patch install.
Subframe connectors would depend on who was providing the connectors, straight install or fabbing up a set, installing under/through floor. All those issues take different time frames.
It's all a time/materials deal to me, what's a decent rate for fabrication where you live $20-30-50-75/hr. I've installed subframe connectors in an hour if the car was ready for them, most of the time it's a 2-4 hour job. Fabbed up connectors sometimes take longer. Minitub can be done in 15-20 and really clean installs can take 30-35, mostly dependent on if the car is torn down to have it done quickly. Pulling interior, panels, etc is a real pain and time consuming. A stripped out car is easier to work on than one that's full interior.