I am wondering why appraisers charge more for land appraisals than an SFR?
Depends on the type of land that your subject is. It has been my experience that with the exception of a residential lot zoned for residential use that most other types of vacant land appraisals are complex assignments and highest and best use is paramount in the determination of value. There can be lots of factors depending on the type of vacant land.
In commercial work, front footage, lot depth, proximity to utilities, neighborhood analysis, environmental (traffic) concerns, just to name a few. God forbid that your subject is part of an assemblage or plotage situation.
In ag work, type of soils, soils permeability, soil structure, soils ability to raise which crops, soil compaction, irrigation water sources, irrigation water cost and restrictions, elevation of property, topography of property, zoning just to name a few.
In subdivision land, what stage of development is the land in, farmland converting to 1st step of subdivision, parcel has approved paper lots in place, parcel has off-site improvements (utilities to frontage of property or does developer have to pay for 1 mile of public utility work to get utilities to site), onsite improvements, roads, streets, curbs, gutter, sidewalks, etc in place, is subject a bulk sale of lots in various stages? I really dislike subdivision vacant land appraisals, developers hide public information and don't talk, afraid the competition will beat them.
Yeah, vacant land appraisals are much more complex than most appraiser think that is why for anything over a single family vacant lot you need certified appraisers.
As for a program. Use Excel and tailor it for your specific subject. I have done many of these and no two have ever been alike.