You said "Did a bit of searching on Pro mtbers salary ranges, seems the majority of the field will earn anything between $150K - $300k a year".
I'm not sure where you found those figures, and I can assure you both I and the riders wish they were true! Cyclists are some of the most grossly underpaid sportsmen & women in professional sports.
I can't comment on DHI because I don't know the riders or their agents well enough to pass an opinion.
On XCO, XCM or even road for that matter, I'm happy to weigh in because I have been in the sport for many years and I do know what I'm talking about. I'm at the events, I'm friends with a number of the riders, I speak to team owners, & I speak to the rider's management agents on a regular basis.
There are a small handful of male riders in XCO who get paid north of $150k per year, certainly none who aren't regularly finishing inside the top 10 with occasional podiums. Further back than 10th and you're looking at $75k-$100k, falling off rapidly from that outside of the top 30 - 40.
The women get paid less than the men.
In XCO there are maximum 5 men & 3 women who earn $300k plus when including endorsements from the likes of Redbull, etc.
Then right at the top you get someone like Nino who is earning north of $1million.
CXM riders are paid far less, there is far less money in XCM than XCO, the same reason XCO riders get paid less money than the road cyclists - there's less money in XCO than there is in road cycling.
Road rider's salaries also have a lot more depth because there is teamwork involved and the teams need good domestiques to form a strong team.
In XCO that is not the case, you have winners / podium finishers, then everyone else who is just filling up the numbers. If one is outside of the top 25-30 places in XCO, you'd be lucky to earn $40k per year. Outside of top 40, you're falling off quickly after that. There are many riders racing at World Cups who are having to work at least part time jobs or still live with their parents into their mid to late 20's in order to pursue their racing dreams.
XCM is even worse, far worse in fact. If you go look at a startlist of an XCM World Championships you will see many riders you've never even heard of, good riders, riders who finish in the top 20 or even top 10 at a World Championship. Why do you think that is? Their federations manage to scrape together some funding to sent them there, but they certainly can't afford to come do an event like the Cape Epic, much as they would love to. It's too expensive for their sponsors or for their federations to fund, so they don't come.
Back to XCO, in my opinion, Discovery/Warner bro's needs to improve on coverage slightly further back in the XCO races to give the riders in at least 10th - 20th or even up to 30th position a bit more coverage throughout the race, even if it's a split screen image every now and then. It's the only way to encourage more sponsorship depth and feasibility for athletes trying to make it in the sport.
The reality is that all +- 80 men and women who line up on a World Cup XCO start line are phenomenal athletes in the top small percentile of people in the world, both physiologically & psychologically. They all deserve to earn a decent wage and get a bit of coverage for what they put themselves through and the show they provide for the spectators, let alone the risks they take while redlining it down technical terrain.