There are plenty of $100-pens that give you the same or better writing experience than many a $500-pen. So if writing experience is the only thing that matters to you, you should reconsider your parameters.
When one decides to acquire a $500-pen one does so, in addition to the writing experience, for the grade of the materials, the quality of the craftsmanship and, whether we want to admit it or not, for the prestige. The Pelikan M1000 ticks all of these boxes, but it's certainly not the only one. Here are some pens that can be found, with varying degrees of ease, for around $500:
--Montblanc 149, another massive pen. Many consider it over-priced. The quality, however, is undeniable.
--Sailor KOP, Japan's answer to the 149. Sailor nibs are second to none.
--Pilot Custom 845. Pilot's BIG pen. The "value proposition".
--Graf von Faber-Castell Classic or even the Intuition.
Finally, my personal recommendation:
-- Any Omas Paragon or 360 piston filler. Omas is gone. However, there are still plenty of options on eBay and FPN, quite often new or in excellent condition. You can still find a full size Paragon or 360 for under $500, but their prices are steadily going up. And some of the most desirable finishes cannot be had for less than $1000.
If you have $500 to spend on a fountain pen, get an Omas while you can. They are excellent writing instruments in every way, and they won't be around for long.