Not really worse than you thought. Bottom brackets are <$25 for just about any generic. Are there plenty for way more dollars? Sure. Yours? Probably cheap.
A cheap torque wrench is less than $30
The bottom bracket socket, (assuming cartridge type bb) is under $20
Boat trailer axle grease is cheaper than dirt. Grease all your threads.
Under $75 dollars in total to do it yourself.
As far as the crank arms go. That could be pricey, but it doesn't have to be. Square taper cranks are out of fashion. Hollow Tech II, GXP, BB30, etc... is all the rage now.
If it were me, before I spent a dollar on anything new, I'd clean the interface area real good, apply a very light coating of grease on the taper of the original bb, slide the crank arm on. Lay the bike on the garage floor, back up the bottom bracket with a block of wood and give it a good hard whack with a heavy hammer to seat it good. I'd use a piece of wood or something to avoid marring the crank arm. Then use a long allen wrench and torque the dickens out of it with my foot. See how long that lasts. If it doesn't you were destined for a new set up anyway.