Jermaine Dupri -- Learns VERY Expensive Tax Lesson

Jermaine Dupri is tax debt free after he recently paid off a giant lien ... but it cost him nearly TWICE AS MUCH as it should have.

According to docs filed recently in Georgia, Dupri owed $493,818.75 in back taxes he failed to pay for the year 2007. But get this ... the principal was only $254,782.64. Here's what the state tacked on:

Interest -- $91,721.75
Penalty -- $64,969.57
Collection fee -- $82,294.79
Costs -- $50 (why bother?)

The lesson here ... PAY YOUR TAXES ON TIME!