yeah the deere suspension kit is like $400-$500 if you buy from the dealer but i got mine on ebay for $100. i put it on myself. it made a night and day difference. my back no longer hurts after mowing those 3 acre yards now lol. they've gone up on the price a bit since then.
i really can't believe they sale a commercial mower without a suspension seat. even homeowner models have springs under the seat lol.