if it fits - great - it might not
mass produced generic real steel holsters are generally a bit slim for paintball markers to fit in - I have no experience with that specific one you linked (at least that I can recall) but you certainly will need to check it when you get it for fit, feel, and quality.
why pay $35 - well few reasons
as mentioned before - fit, feel, quality are important
if it was made by a custom tailor - labor costs are higher, material costs may be based on quality of material.
Honestly in the grand scheme of things - $35 for a GOOD holster is not much to pay at all - some of my real steel reside in custom leather that cost me closer to $85 to $135 for those rigs and to me it was worth every cent.