I have created several fonts over the last year or so using a program called Font Creator. I generally spend anywhere from 4 hours to as much as 16 hours to produce one very limited partial font. In that time frame I can usually produce the upper case, lower case letters, and numbers if I see fit to go that far. It's just a hobby for me and I draw all of my letter forms freehand right inside the program, no sketched renderings, scanning, cleaning up, importing, cleaning up more, fine tuning, etc.
I can honestly say there HAS to be much more that goes into the creation of professional fonts, especially those that have gained fame for their style and beauty, and especially those that are rendered from hand drawn or hand painted letter styles, scripts in particular. I tried to sit down and create a script font freehand in the program and I got burned out on the project and swept it under the table by the time I got into the third character. So all in all, while I would say that some fonts such as simple sans serifs may be created within a matter of a few days, other fonts, such a scripts would take much, much longer. Weeks...months...years? And I guarantee you even the simplest font, when calculated into a precisely rendered family of fonts, can absolutely take years to create. There has to be literally thousands of characters in some families.
I'm sure any professional font maker would look at my stuff and say that while it looks okay and the idea is there, they could use a lot more time invested...time that I certainly don't have to fine tune the characters and extent the amount of available characters.
I am posting some examples. I have probably less than 100 hours invested in all of these, but most are missing lower case letters, numbers, and punctuations. And don't even get me started on ligatures and other glyphs because they simply don't even exist. These work for what I need them for, but could use a ton more work. I would say $15.000-$30,000 in man hours can certainly be a fair assessment for some fonts.
As far as how much we spend on fonts, we haven't invested much yet (we have been in business for 14 months) but have been planning on it for some time and will be purchasing some in the very near future. Some may recognize my Union Slab font as a striking replica of House United Slab. That's because it is. We do so much heat transfer on school apparel and I really wanted to own that font family, but we weren't in the financial position to buy it at the time so I took it on as my own project. I liked my knock-off finished product so much I went so far as to create the bevels, which would look awesome as a double layered heat transfer.
My background is Signs but I retired from it to do what I love which is hand lettering and type design. 