How Do Ancient Coin Collectors Or Numismatics Make Money?

My view, is yes you can make money but it will not come from buying very easy. You will have to be relentless in your searches and dedicate a lot of time in researching what to look for when it comes down to quality and value.
Be prepared to make some mistakes and gradually narrow down you search to something you enjoy and can easily spot when you come across it.
But yes it is a hobby also and you should buy things you like, so if it doesn't sell you would be ok in holding on to it.

I look at an auction pre view on line first, before attending an ancient coin auction view day.
Also, before attending the view day, I do a lot of 'due diligence' with price research for those lots I may be interested in.
I select only one or two lots, and submit single fixed low bids for those lots. I never attend the auction, so I never get involved in bidding wars.

With such a practice, I only have about a 30% success rate; that's OK, but at least it means I can always get coins that I may be interested in, at good price.

THEN I keep them. The last time I sold a coin out of my collection was more than 40 years ago.

How do I make money? I don't, but the value of individual coins over a long period of time has increased by many multiples.

Similar to building a superannuation portfolio, but I will never receive any benefit. However, my kids will, when they re auction the collection after I die. That has been written into my will.

In economics classes we are always taught that the true value of an item is what it sells for in an auction situation. That is the price a willing buyer will pay for an item a willing seller is offering for sale. Given that coin collecting (and coins) are a dying hobby (check the age of the average collector), the likelihood of prices rising over time is slight to none.

Granted some items may rise in interest and the overall supply may drop due to damage or destruction but the demand (interest is most likely to drop far faster. And within the general trends one MAY be able to trade well and succeed at buying low and selling high(er). BUT most of the "gains" collectors feel they are 'earning' are unrealized and when they (or their heirs) actually try to sell their collections reality comes and bites them (Except that most heirs have no previous thoughts of what the "value" of the collections they now possess and they take the price offered .. which is less than the departed collector was estimating his inventory was worth)
So in short unless the metallic value hits another pea; you better enjoy this as a hobby

I would describe my collecting attitude as "Taklamakan style": coins go in, they don't come out again.

The exception is when I (usually accidentally) purchase a duplicate, in which case, whichever one is second-best is sold. I usually sell them at my local coin club auction, and am happy to make a loss on them. Fortunately, it is actually rather hard to obtain "duplicate ancient coins" by my definition, so for ancients this doesn't usually happen to me. I think I've sold three ancient coins in my entire life. (I have bought and kept 437 of them.)

I am not in the business of buying and selling but I have a few thoughts.

1. If you have a premises it may be quite possible to buy items at less than their value. Pawnbrokers and other shops often offer very stingy offers because they hold the cards, often the person wishing to sell is low on options and will accept low offers. If you buy anything for less than its worth you should make money on it.

2. Some people have items on ebay for way more than can be justified but I guess they occasionally get lucky and sell them. Others price far more competitively but sell in large volumes which is OK if they have access to lots of stock.

3. I would hope to make some money long term by virtue of the fact that I don't flip items. Given that money devalues and rare items only get rarer if you buy good items and sit on them for a long period of time one would expect them to increase in value. When I am a pensioner maybe I will be selling items rather than buying them.

4. You can earn money from knowledge... if you see things that others don't (like a rare coin within a lot) or buying unidentified bulk lots and identifying and selling separate there could be potential.

5. I am sure we all heard about someone trading a paper clip up until they had a house? Repeatedly doing trades which are in your favour is another way people build value.

I don't want this hobby to be one that makes me large losses, how you go about things in terms of investment is quite different from the collector mindset (that you need to fill gaps regardless of cost) so internally often I am at conflict with myself. I figure what I lose on the swings I win on the round-a-bouts. Definitely some of the items I have bought have increased in value and others have cost me but across the board I haven't done to badly.