Maybe the problem isn't in their cost but at the way local ASN's are making regs reform.
Only in Argentina and Brasil MR were really promoted as the rally top class, but in Brasil's case that option was somehow undermined by XRC tech choices (it came with a heavy 3.6 V6 and are made by the company of the running champ, Mauricio Neves). Bolivia has an open proto class (Dytko protos are dominant but I believe an MR Fiesta was lately imported) and Peru rally scene seems a mixture of rally and cross country events, with no place for modern rally cars. Uruguay is still finding the way to replace N4, while Paraguay introduced FIA regs (R5/S2000) and Chile also uses FIA regs but emphases renovation into R2/R3 cars.
MR success depends on the ability of national turners build them locally. That's the best way to keep them cheap, as the Argentines has managed to prove.
MR Argentina action:
https://www.youtube.com/watch?v=ZB6ODEv6PEk
Neves 207 XRC:
https://youtu.be/phfWeVA7dUk?t=262