Comparative cost effectiveness analysis requires estimates for the causal effect of treatment on both cost and effectiveness (e.g., survival). However, joint modeling of cost and survival are challenging due to censoring of total costs, censoring of survival times, zero-inflated outcomes, skewed outcomes, and confounding. Here we propose a joint model based on a gamma process prior for survival and an enriched Dirichlet process prior for costs. Marginal estimates of causal effects are obtained after integrating over the marginal distribution of confounders using Bayesian bootstrap. This approach enables inference on the joint posterior of cost and effectiveness. The methodology is illustrated using data on cost effectiveness of cancer therapies.