I'm pretty sure I am opening a can here as this can be a heated topic. Do I have some expensive pens? Yes, yes I do and I have cheap pens as well. So this post is purely my opinion and not based on any facts other than my own experiences.
I guess I will need to set boundaries here to differentiate between inexpensive and pricey. To me, inexpensive falls in the up to the $50 - $60 range where as the expensive pens are going to be $200 and up. The in between is dicey but I'll address it.
I have a Twsbi Diamond 580 with a 1.1mm stub nib which is around $55 and I also have a Visconti Millenium Arc Moonlight Green with a 1.3mm stub which was around $350. To me, the Twsbi out performs that Visconti by 10. The Twsbi is a smooth writer with a steel nib, very pleasant to use and has a large ink capacity as it is a piston filled pen. The Visconti is a Chromium nib and is smooth but is hampered by baby's bottom on smooth paper like Rhodia or Clairfontaine. It is a crescent filler with a much smaller ink capacity than the piston filler and ink tends to pool under the feed when writing.
So the Twsbi is better right? Well, yes and no. The Twsbi writes better for me and stores more ink as well as being affordable. The Visconti writes well on toothier paper but has other qualities. It is a limited edition pen and only 200 of each color were made. It is also amazingly gorgeous with the resin used and those swirls are mesmerizing. It also feels rich to the touch. In other words, I paid for the name and the aesthetics which I am ok with.
What I am saying is that it is not all about price when discussing fountain pens. What they are made from, their design and the nib material all factor in. The pens are functional but the expensive pens tend to be more luxurious but that does not make the cheaper pens less valuable. I have 5 different Jinhao pens which retail anywhere between $5 - $12 and I love them as they write very well and still look great.
It is all in the eye of the beholder and what appeals to you. I have 2 pens that are made of copper, yes, solid copper. One is a Karas Kustoms Ink which is $175 and the other is the Montegrappa Copper Mule which retails for $375. So what affects the difference of $200? Both pens are made out of the same material and both pens are machined meticulously. Both pens write incredibly well and have a nice heavy weight, which I prefer. The only thing I can come up with is the Mule is made in Italy by a luxury brand whereas the Karas Kustoms is made in the US by a newer company. The Mule is shipping a limited edition copper mug with the first installment of pens for a small amount of units and the mug sold me...I will admit it. I love that mug and I know it was a gimmick but I found it to be worth the price as I did buy it.
Pens are much like anything out there. Do you buy a Chevy or go for a Corvette? Can you afford either? Would you spend the extra money to get the sporty vehicle? The point is it is your choice and your choice alone. If you find the value in the cost of a fountain pen that appeals to you, whatever that cost may be, then it was worth the expense. Not all pens appeal to all people and that is why there are so many to choose from.
Don't get sucked in by a brand name though, if you are new to the fountain pen world. Try to find more information online as there are a lot of reputable reviewers out there. If you are fortunate to live near a pen store, visit it and try the pens out. It pays a lot to try before you buy to see what you may or may not like. Go to a pen show. That is the great opportunity to see a whole multitude of pens in a single place. Find other enthusiasts in your area or on a forum like Reddit. A name brand may work for some people but it may not be your cup of tea.
You and you alone can dictate the value of a pen. If you want to pay the price then it is worth the expense. Plain and simple. I cannot stress finding a way to use a pen before purchase as then you know if it works for your tastes. Fountain pens are to be used and cherished, they are extensions of your thoughts and creations. You set the price.