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Job well done! I tried reverse engineering the encryption on Yamaha's midi files. I thought it would be super complex but it turned out to be ridiculously easy. It's funny when you're preparing mentally for some long slog and turns out to be an hour at best. In case you're interested: they used a fixed block of 256 bytes that they xor'd the data with in a cyclic fashion.

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That's more like obfuscaton, you got lucky there!

I've reverse engineered lots of things, but the one time I actually got paid for it (this is more a hobby to me), I got the exact opposite of what happened to you.

I quoted some small amount to document the protocol to configure some embedded device that I thought would take a day or so, and it turned into a two-week nightmare. Turned out there was no configuration protocol, it was firmware updates always -- and internal parameters were just overwritten along with the code. So I ended up having to disassemble a big chunk of the firmware before I could configure the device.

Pro-tip, state your assumptions baked into the estimate. If one of them is wrong you can renegotiate price, although depending on the client, you may not always want to do that to show good will and whatnot.

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