I am slowing using up my slide film also. A roll of 35mm Kodak E100 cost equiv of £16 and then £13 or $16USD for processing here in New Zealand.
What I have done is import film from B/H or Freestyle in the USA and pay $10US for freight and then send it back to the USA in batches of 10+ rolls for processing. The 2-way post is probably $50-60US. E6 chemistry are not available here and the USA does not post it out of the USA (ORM-D). For the at least the last 10yrs all the labs here no longer do slide mounting, when they used to do it it was 60c USD per slide times 36 frames for each roll. We have no pro labs here anymore that does dip dunk, there is one maybe 600 miles away. The local pro lab we had was sold away and the first thing they did was get rid of the film processing unit, they only wanted their lambda printing machine. Maybe for some time we didn't have any E6 processing here, because that lab got rid of it and the other lab here only did C41 and B/W and only due to a earthquake at a different city they bought their E6 machine.
Germany does but it is very expensive and they do 3 monthly shipments a year. I am currently down to 2 partial rolls of Provia and 1 Provia and 1 Velvia left in medium format. I was given a bulk roll of expired Fuji MS 100 but might test a roll out and then sell it ...
I've struggled with slide film because I like to shoot in low light with a tripod. Due to the limited dynamic range the night time cityscapes doesn't look at nice. How did professionals shoot night scenes, did they use slide film? Ie skyscrapers with a deep twilight blue sky and the traffic car streak lines.