$15 for fluon once off doesn't seem expensive when you put it in the context of saving $5 (or whatever you pay - I've never ever bought insects from a pet shop and haven't taken a look at prices for years) every single feed.
Woodies are extremely easy to breed, take literally about 2 minutes of maintenance per week plus a six monthly clean out (I've left colonies years without cleaning them) and virtually nothing in ongoing costs. I used to produce enough to sell kilograms of them and it cost me less than $1 per week to feed them, and most of that cost was carrots for moisture. Before I realised I could sell them I used to freeze the excess and put them on the compost heap because they just bred like crazy.
They actually save you a lot of time as well as money because they save you a trip to the shop, which takes far longer than tossing a piece of carrot in once or twice per week. You always have every size you need on hand rather than having to go to the shop every time you need to feed your critters, which is a huge benefit, they don't make noise, I spent years producing them just in little 10 litre tubs (with only about 5 colonies in small tubs I produced enough to feed literally hundreds of lizards and frogs!).
Not sure if he's still doing it, but Brian Barnett used to sell large numbers of woodies in the western suburbs (Ardeer).