In fines and reinstatement fees alone, a Missouri DWI conviction may cost you in excess of $5,000.  You must also take into consideration that you may lose your income if you are fired from your job and that your insurance premiums will skyrocket once you file an SR-22.

Consider also that, if you injure or kill someone, you are facing a civil lawsuit and can be ordered to pay damages. 
Finally, if you hire a Missouri DWI Attorney and beat the charges, you can still expect to pay $2,000 or more in Attorneys fees.