Make sure you get a price in advance. You're buying the 'showcase experience,' so be an informed consumer and understand what you are getting and how much it will cost. Are lessons included? Rehearsals? Choreography sessions? Guest tickets? Hair and makeup services? A video? How many performances will you be dancing? And so on. "Showcase" can mean different things at different studios.
The last showcase I was in cost about $1500. This included 10 private lessons, 2 sessions with a choreographer, 2 full-cast dress rehearsals, professional hair and makeup services, a DVD of the entire performance, two guest tickets, and a cast party. The showcase was held on stage at a local 500-seat theater with professional sound and lighting. We danced two performances (Friday night and Saturday night), and both nights the theater was full. It was all very professional and very well-done. The show had a theme, an actual director, and so on. I would like to do it again some day but I'm competing now and so have other things I'm focussing on.
Our studio also does smaller "in studio" showcases that cost less. It's been so long since I've been in one of these that I can't recall how much it cost, but it was also a big deal with lighting, sound, multiple performances, hair and makeup, etc.
Other studios in our area have very simple showcases where students just basically dance their competitive routines with their teachers at an afternoon or evening party. These range in cost from $5-$25 per dance (plus a per-dance fee to your teacher, if you are dancing together, for his or her time). These showcases don't include lessons or anything else special like that.