Never been in the position to buy an exotic, but i'd say its a lot to do with emotion. If you love the way it looks, drives, and sounds go for it. Its always going to be difficult to justify looking purely at the numbers
Alternative exotics in the $100k range I'd look at an F430 (although nice ones seem to be more like $120k), sounds like you want something faster though. Alternatively an R8 V10 or earlier Gallardo just for that heavenly V10 soundtrack. The MP-4 12C is awesome but given its technological complexity I'd be afraid to run one out of warranty.