East River and West River are different markets
East of the Missouri, South Dakota is row-crop country with soils and rainfall supporting corn and soybeans, and prices track farm economics accordingly. West of the river, the land is predominantly rangeland, valued on carrying capacity and priced far lower per acre.
A buyer comparing per-acre prices across the state without accounting for this is comparing different assets. Establish which side you are on and value accordingly.
Rangeland fundamentals
On grazing ground, the relevant measures are animal unit months, water development for livestock, fence condition, and whether the parcel is a workable unit or a fragment requiring cooperation with neighbours. Grass condition and species composition matter to carrying capacity and are worth a knowledgeable eye.
Ask about existing grazing leases, whether they survive the sale, and what the terms are.
Water permitting
South Dakota requires permits for most non-domestic water use. Irrigation development depends on permit availability from the relevant source, and in some areas appropriations are limited. Confirm what water rights, if any, attach to the parcel and what a new permit would involve.
The tax picture
No state income tax is a genuine benefit for a resident owner. Property taxes are the offsetting cost and vary by county and school district. Get actual tax bills rather than estimates before budgeting holding costs.
What to verify
Grazing lease status and terms. Water permits and livestock water development. Fence condition and boundaries — a survey matters on large rangeland parcels where fences may not follow lines. Legal access. The risk scorecard for the rest.