Wow, overstaying by 3 years. They surely will be very surprised. Overstaying Schengen visa can be very costly. The amount of fine depends on the judgment of the officer. 700 EUR fine after 20 days of overstaying Schengen visa in Greece, 550 EUR for overstaying their Schengen visa by two months in Switzerland, 100 EUR for overstaying by 3 months in Germany, another case of 600 EUR for overstaying Schengen visa by 30 days in Switzerland, etc. The chance is also that you migh not be allowed to get back to the state or even the whole Schengen zone for up to 5 years. See here for more:
overstaying Schengen visa Hope this helps. Let us know your experience.