[jandrese]

I'm really surprised that board is only $3 given how expensive off the shelf inverters are. I would think there would be enough competition in the pure sine inverter market to drive prices down, but I guess it's just small enough to not function optimally.

[crote]

The $3 part is only the controller, though. It doesn't actually handle the power itself - it requires extra components for that. It'd be like saying a $100 microwave is expensive because it is controlled by a $0.50 controller chip.

The project page itself states that the inverter will cost at least $20 in total - and that's using essentially the cheapest components you can find. Once you use quality components and include things like proper input/output protection, connectors, and a casing, you're likely looking at a $40-50 BOM.

A $150-$200 retail price is very fair, considering all the other stuff you need to pay for to actually design, certify, make, and sell a product.

[megous]

Just the tranformer costs at least $250-300 unless you get it second hand.

[samtho]

For this level of hobby project, there is no need to buy that new. I would either wind my own transformer or (more likely) go to the computer surplus store, get a battery-less UPS and pull the transformer from that.