There are too many variables to give an honest response to your inquiry. I'm gathering no plumbing (mistake in my opinion since you're planning a bar) but what kind of electrical (outlets and lighting/switches) do you want? Studs on 16", or 24"; metal or wood? Insulation? Drywall or drop ceiling?

I recommend you develop a plan. Recently I saw a software package at a computer supply store for about $40 which offered a way to design a space and give a materials cost. You might want to look into something similar as whether you anticipate DIY or contractor, you need a plan. I've seen local roadside posters advertising finished basements for $18/sq. ft. but I have no idea what might be included or the quality of craftsmanship but I suspect minimal.

I'm linking our basement which you may have seen before. It was entirely DIY and completed about 5 years ago. The bathroom has never been built and I haven't totaled the receipts but my best guess is $15,000 for about 700 sq. ft. (finished) with quality materials, robust electrical, kitchen with appliances/cabinets, supplemental heat and functioning plumbing all to code.

Hope this helps. Good luck.

Here is a link that might be useful: Basement

It's been a few years since I was doing it professionally but we charged somewhere between $28 and $33 per square foot not including flooring.

I resisted putting a bathroom in the basement since there is one at the top of the stairs. My DH insisted and $6,000 later we have a half bath down there.

I am happy we have it since it is our only source of water down there.

We are finishing our basement right now. We are doing a lot of the trim work ourselves. Painting and putting the floors on. We do have a bathroom down there but it was already plumbed for a bath so I would say it added $2000 including plumber and fixtures. We are looking at it costing us $12,000. We hired out a small portion of the framing (my dad framed out most of it-he's a carpenter but lives out of town or else we would have him do all of it). We also hired out, electrical, plumbing and drywall. We did all the other stuff ourselves.

I just got mine done. About 600 sq ft, basic. No bathroom, wet bar etc. Just one big room. Total cost including materials was $13000. Of $13000, electrical was $2500, flooring (tile) was $2400. Rest includes waterproofing paint on concrete, framing, drywall, ceiling, closet doors, trims, painting etc.