Personally i have no idea of why people value domains like these so highly, its not like the number is easily remembered nor is it linked to something that could be, i think unless you can create a brand with it, you're looking to break even on the reg fee.
reg fee?..you can't even think to buy it for 50$...so please no such comments on reg fee...About idea..you don't have but others have..3 letter is easy type domain.
Mate, you are coming into an online community and asking opinions of thousands of users, not all are going to pat you on the back and tell you that you're sat on a goldmine, end of the day my opinion is that if you get offered $40 for the domain, let alone $50, snap their hand off and think yourself lucky.
of course you say that because you are on appraise side ..but if u have this domain will think different..OK..then why on this domain were so much bidders on auction?are they think like you?