Lot's of things to consider when putting up a pole building, and price is definitely one of them, but not the only one. We built a 24 x 32 building in 1993 and if I had it to do over again I'd probably go at least 32 x 48 knowing what I know now. You'll fill your pole barn to whatever size you put up, so try and build the largest you can now. I saw a package deal over the weekend comparable to the building we put up in 1993 (T1-11 siding, shingle roof, 4x6 poles, sliding main doors, one entry door, no windows) for about $4,800 from Central Michigan Lumber (Lapeer, MI), delivered to the site within some number of miles.
Overall size: not just length by width, but also height. We have 9 ft. clearance inside the building with 8 ft. doors. OK for my use, but you need to consider whether 10 ft. or 12 ft. sidewalls will better serve your needs.
Doors: need to think about access to the building itself. Generally, more doors mean easier access and often times better utilization of floor space. Also, do you want sliding doors, overhead doors, or both in different areas of the building? Entry doors also need to be part of the thought process.
Siding/Roofing/Insulation: steel sided buildings are pretty common, although lots of folks use T1-11 cedar siding for appearance, and many use particle board covered with vinyl siding. Some folks use steel roofing, while others use shingles. I like a shingle roof....seem to get less condensation and it's quieter when it rains. Insulating all or part of a pole building gives you options as far as a heated workshop area or an area to keep the tractor so it'll start when the temp is real cold.
One story or two story: two story pole buildings give you lots of options. A gambrel roof provides a great storage/workshop area. Single story buildings are generally less expensive to build and finish.
Floor: what are you going to be using the building for? We put in a floor consisting of a sand base topped with road gravel. It's packed into a rock hard floor that is basically no maintenance. A cement floor costs more, but has a lot of benefits....even if you only do part of the building in cement initially.
All of this to simply say, you need to figure out what you want before you get too far into pricing. Talk with local lumber yards...most have pole building packages that can be customized to meet your needs. Also, they know of reputible builders that will put them up for you. And, if you can muster some help, putting up a pole building can be a lot of fun. Try Home Depot or Lowe's for info on pole building construction. I've seen a variety of books there on different building plans and pole building techniques.
Just like buying a tractor, once you nail down what you want, you can then compare prices from different sources to get the best deal for you.
Good luck.
Bob Pence