Without meaning to sound facetious, or be negative towards the up and coming ACDC pinball.. but $7250 up front sounds very like the total cost an ACDC LE before a comission is charged... and its unseen???... I cant get my head around that   
Deposits are normally unrefundable and given to prove that you will honour the final transaction... if you dont.. deposit gone, and thankyou, you covered my costs ( somewhat). 30 - 50% is the norm depending on the job... can honestly say, ive never charged more than 30%.. even on a $50K job