The high end prices on eBay are only for the throw away cardboard box. The game with sleeve, manual and case has been selling for $30 - $40 on eBay.
If you want to pay more than the price of the game in case extra, just for an extra cardboard box, then $75 is actually an average eBay price right now.
ProTip: when checking game "values" on eBay, click on "sold items" to see what has actually sold. If there aren't many results, click on "completed listings" to see what prices are too high for the game to sell at. Most importantly of all, pay attention to what each listing actually includes and the condition of each individual piece. If a mint/complete copy sells for as much as $75, a complete copy with a worn box and/or manual is worth maybe $40. Otherwise you're literally paying a premium for garbage, instead of a premium for premium condition.