ID V     value     weight
   A 1  8723.286 0.12183436
   A 0  8889.905 0.09787817
   A 1 14984.370 1.00000000
   B 1  8176.189 0.12183436
   B 1  8342.808 0.09787817
   B 1 14437.272 0.18412047

ID  V      value        weight       output
     A  1   8723.286    0.12183436  8869.605081
     A  0   8889.905    0.09787817  8869.605081
     A  1   14984.37    1.00000000  8869.605081
     B  1   8176.189    0.12183436  10998.48252
     B  1   8342.808    0.09787817  10998.48252
     B  1   14437.272   0.18412047  10998.48252

dat <- data.frame(
        ID = rep(c("A","B"), each=3),
        V  = c(1,0,1,1,1,1)  ,
        value = c(8723.286, 8889.905, 14984.37, 8176.189, 8342.808, 14437.272),
        weight = c(0.12183436, 0.09787817, 1.00000000, 0.12183436, 0.09787817, 0.18412047)
      )

    dats <- split(dat, dat$ID)

ifelse(dats[[1]]$V[1]==1 & dats[[1]]$V[2]==0, dats[[1]]$weight[1]*dats[[1]]$value[1]+(1-dats[[1]]$weight[1])*dats[[1]]$value[2], NA)

ifelse(dats[[2]]$V[1]==1 & dats[[2]]$V[2]==1, dats[[2]]$weight[1]*dats[[2]]$value[1]+(1-dats[[2]]$weight[1])*((dats[[2]]$value[2]+dats[[2]]$value[3])/2), NA)