Bank checks cannot be made anymore and don't fetch much more than face value still. The exception to that are the 0 gold checks(and 666 gold checks) because they are a bit more rare(or evil). Still, I haven't seen even those sell for more than 250k and the 1m ones go very slowly at 1.1m. There are exceptions, someone will undoubtedly want a lot of them for a new deco project and at that time will pay more... but don't hold your breath for that to happen.