How much do cylinoids for a transmission cost?

I have a 2003 Mitsubishi Montero Sport. The transmission starting slipping recently. I had the transmission fluid cleaned and it is still giving me trouble. I am bringing to a transmission specialist that gave me a worse case scenario of $2500 - $3000 for a new transmission. But he said that it could also be the cylinoids which would be a less costly situation. If it is a cylinoid, usually how much does it cost to repair, and is it just a "bandaid" like fix or will this usually do the trick? (I am hoping to keep the vehicle for only another 6-9 months until it is finished being paid for.) Thanks in advance!