I am not sure where we get inflation values from but $1100 today at 3% inflation (which is much higher than real inflation today) will cost $1350 10 years from today and not $1600.
If you purely look at it from an investment perspective I would like someone to recommend me a banknote that I can purchase today that will give me 7% per annum compounded total return for the next 10 years. I am willing to lay a firiendly wager that if the note increases in value by more than 7% the person who recommends it to me keeps the excess but if it makes less than 7% they pay me the shortfall.
Surely if I can find a radar or a solid or a low serial number note in circulation or through a brick search I can instantly make the money but if I purchase it at the going rate my return in future years will not meet my expectations. For example if I purchased a $5 replacement at $25 today to meet my objectives it would have to sell at $49 in 10 years for me to realize a 7% return. Have replacements bought at fair market value in 2003 doubled in price today. If this was the case similar replacements (in terms of rarity) from 2001 would be selling at twice the price of replacements from 2012. The reality is that they are selling at about the same price e.g. $5 journey notes from 2003 v/s $5 journey notes from 2010 with similar print volumes are about the same price in Charlton.
IMHO there is no intrinsic dollar value in banknote collection other than face value and therefore future values can only be predictated by the vagaries of market place. At best any investment in banknotes would be considered a high risk investment and therefore speculative.
IMHO the only people who consistently make money in selling collectibles are those that make a business out of it, those that make supplies for collectibles and those that inherit or get lucky and run into the collectibles at below market prices.
The rest of us who may not make money can at least strive to enjoy what we collect. Once in a while we may get lucky and hit a jackpot but only if there is someone else willing to buy from us because they want to enjoy what we might have.