Precise tuning is nothing our vendors can really do amidst the sound of honking horns and such in the open air shops and markets of India, but we can do it very well in our quiet shop here in North America. Re-tuning an entire instrument to A432 requires extensive scraping of every single reed, going back through after it settles, refining, etc. It takes time to get it stable and proper, and that's why a fee is added for this service. If you're experimenting with A432, this added layer of service gets you what you want*. If not, the extra service is not necessary.
*NOTE: Once a harmonium is tuned to A432, you cannot tune it back up. Tuning to A432 leaves your instrument approximately 1/4 step flat from traditional Concert Tuned instruments, which will sound "out of tune" when compared to these instruments.