Antelope can readily be hunted as a DIY thing. Success rates for antelope are over 90% in Wyoming. I was told before I went out that the antelope in unit 23 where I was hunting were as plentiful as grasshoppers. I thought they were joking, but they were not. Unit 23 is easy to draw in, but not much public land. I paid $100/gun for my son and I to hunt on a 1,200 acre ranch. Other such options are available.
There is a large public land area south of unit 23 called the Thunder Basin National Grassland. I forget what unit numbers are in that grassland, you would have to check a map. It seems that it is necessary for a non-resident to have 1 pp or even 2 pp to be drawn in that area, the last time I checked. I want to hunt there in the future and am collecting preference points. I'm planning to do this some year that I don't go elk hunting, but lately I'm going elk hunting every year. Maybe when my knees give out: I'm 58, so that day is coming.
I would not expect to find antelope with big horns in the hunting units that offer lots of permits and/or require less than 5 pps. I'm not a trophy hunter, so this doesn't matter to me. It is not an accident to bag a pronghorn in Wyoming with exceptional horns: it is a matter of knowing where the units are that contain such animals (probably related to genetics, carrying capacity of the land, and the hunting permit allocation policy for the unit). My guess is in most instances outfitters have figured this out in advance and have exclusive hunting access tied up with the appropriate land owners. I'm just saying if you are looking for a "trophy" pronghorn it is complicated and you aren't going to stumble over one.