Ground mounts are far more expensive, not only because of how strong they need to be to support the panels under strong winds and snow without deflection, but the anchoring can be complicated depending on the site.
Some people can just hammer spikes into the ground, fill with epoxy, and their array is anchored. For my yard, I have to dig 4-feet down below frost line, through incredibly rocky clay soil, and bury (and concrete) 4x4 posts. On top of those posts goes the (expensive) metal rails to mount the panels. For just 10 solar panels it's gonna cost me ~$1000 in materials and many hours of digging.
The metal U-channel rails I'm looking at using will cost around $40/pp (10-ft), and I need at least 10 of them. In theory a cheaper option could be wooden boards like 2x8/2x10, but they're significantly heavier, bulkier, and would still be difficult to mount to.
This construction lets me build the array however I want, including adjusting angle (I'll have 4 pre-set angles for each season). This design is still cheaper than the cheapest pre-fab ground mounts, which are metal legs which go for ~$110/pp. You need ~2 legs per panel, though in some cases you can share one leg for two panels. For 10 panels you still need at least 11 legs, so at least $1100, before cost to anchor them. And that's a fixed angle. The adjustable angle ones are more like $185/pp.