This is not as robust as a lift kit with a professional grade router, but can be assembled for under $100 (As low as $70. One commentor has noted that HF also sells an identical plate for about $20 +$7 S&H.)
(Note: As usual, this will probably void your warranty.)
Step 1: Design Overview
Step 2: Depth adjust replacement
A tee nut anchored to the motor housing, about 8" of threaded 1/4-20 rod, a 1/4-20 coupler, and a "Connector bolt" (unseen below the coupler) through the bottom base.
Total required parts: One 1/4-20 x 40mm(1.5") Connector bolt ($3.50 for 4 in the Furniture parts drawer at Lowe's), 8" of 1/4-20 threaded rod, 1 Tee Nut ($.70), and one 1/4-20 coupler( $.85 each)
(Skip the washer as it is unnecessary. )