PCA at the moment is a technology maturation and demonstration program, and thus not directly comparable with the B-21. The bomber is also much less ambitious and a lot of work and money had gone into it before contract award. When you include the R&D for the cancelled next generation bomber it was around a few billion according to the contract announcement press conference. So eight years from today is not a credible date for PCA IOC. The figure the Air Force has been floating is around 2030, and in aerospace the schedule often, if not always, moves to the right.The IOC of the PCA/NGAD will come faster. The reason being that the RCO is involved in running the program, not the usual USAF procurement. They are modeling it after the LRSB. As for not having funding:
The total request was for ~$492 million FY19 (just passed). The projected FY20 is showing a $1.3B request and a projected $1.9B in FY21 and $3.2B in FY22.
The B-21 is going to take 8 years from contract to IOC (if they can keep the schedule). There's no reason a PCA couldn't do the same.
For historical comparison, the ATF spent $3.2B through the production of the 4 prototypes in now year dollars (adjusted for inflation).
The NGAD budget NOT strictly a development budget. Something(s) is being produced for $3.2B.
The F-22 was originally going to IOC in 1995, but was delayed for budgetary reasons (Cold War was over, Peace Dividend, etc). The F-35 took so long because it was so ambitious. They really made three different aircraft that shared parts and winked at Congress. Making sure all the parts worked together was part of the problem (others being bad management and stupidity in adding more requirements after the contract award, always bad that).
Assuming the PCA/NGAD sticks to the B-21 script, it'll come far, far faster.