If you stay w/in factory guns, there's not much difference in price between caplocks and flintlocks. But if you get into semi-custom or custom flintlocks, the prices are determined by the maker, components, style and supply and demand. The only caplocks that approach the average flintlocks are well built Hawkens.
Most well known builders have extended delivery times, so lesser known builders get orders from impatient customers....this is sometimes a good thing but sometimes doesn't work out.
I just sold a spec built Bucks County flint LR for $5000 and I'm not a well known builder, but advertised it for 7 mos, not really caring if I sold it at all. All of a sudden 4 people were interested in buying it and the eventual buyer didn't quibble over the price. The reason for all the interest was that if was tax refund time. So...if a lower price is wanted, don't shop for a flintlock at that time of year.
Used flintlocks can be a "good buy" or not....a good presale inspection is a safeguard for buying a quality, used flintlock.
You didn't state the price range you're willing to spend, but the many options should satisfy your needs......Fred